fix(correctness-bundle): I16 correctness fixes + dead code removal + ruff clean

N1: COM hatch non-associative (AddHatch associativity=False)
N2: ezdxf refuses DWG saves with clear error; server.py derives fmt from extension
R19: dimension_aligned dist→distance; dimension_angular correct add_angular_dim_2l args (base/line1/line2/location)
R9: polar array 360° no-duplicate (divisor=n when fill_angle%360<ε)
R13: entity_offset side_x/side_y honored in ezdxf via cross-product (LINE) and distance-to-center (CIRCLE)
R18: drawing_new bootstrap failure surfaces status="degraded" instead of swallowing silently
Dead code: engineering/section.py, gear.generate_tooth_profile, CommandResult, _ACI_NAMES, set_layer_active, ensure_linetypes, ComBackend._batch_mode instance attr, engineering/__init__ build-seam comment
Ruff: 38 auto-fixed + 5 manual → codebase is now ruff-clean; CI lint is now blocking

184 tests pass.

engineering/__init__.py

@@ -6,7 +6,6 @@ from .gear import (
     draw_spur_gear_front_view,
     generate_full_gear_outline,
     generate_involute_flank,
-    generate_tooth_profile,
     involute_xy,
 )
 from .keyway import (
@@ -32,23 +31,8 @@ from .plan_spec import (
     SheetSize,
     SnapType,
 )
-from .section import apply_section_hatch, cutting_plane_line
-
-# Agent B contributes titleblock + validator. Imports are guarded so this
-# package remains usable while B is still in flight; once those modules land
-# the symbols flow through transparently.
-try:
-    from .titleblock import TitleBlockMetadata, apply_iso_a3_titleblock
-except ImportError:
-    TitleBlockMetadata = None  # type: ignore[assignment]
-    apply_iso_a3_titleblock = None  # type: ignore[assignment]
-
-try:
-    from .validator import DrawingValidator, ValidationFinding, ValidationResult
-except ImportError:
-    DrawingValidator = None  # type: ignore[assignment]
-    ValidationFinding = None  # type: ignore[assignment]
-    ValidationResult = None  # type: ignore[assignment]
+from .titleblock import TitleBlockMetadata, apply_iso_a3_titleblock
+from .validator import DrawingValidator, ValidationFinding, ValidationResult
 
 __all__ = [
     "draw_helical_gear_front_view",
@@ -56,14 +40,11 @@ __all__ = [
     "draw_gear_section_aa",
     "generate_full_gear_outline",
     "generate_involute_flank",
-    "generate_tooth_profile",
     "involute_xy",
     "draw_keyed_bore",
     "draw_keyway_section",
     "keyway_dimensions",
     "DIN6885_TABLE",
-    "cutting_plane_line",
-    "apply_section_hatch",
     "ENGINEERING_LAYERS",
     "STANDARD_LINETYPES",
     "ensure_engineering_layers",

engineering/critique.py

@@ -34,7 +34,7 @@ _DIM_TYPES = {
 }
 
 
-async def _check_iso128(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_iso128(backend: AutoCADBackend) -> list[Issue]:
     """Layer lineweights must be in ISO_128_LINEWEIGHTS_MM (or -3=ByLayer
     sentinel meaning 'inherit')."""
     issues: list[Issue] = []
@@ -69,7 +69,7 @@ async def _check_iso128(backend: "AutoCADBackend") -> list[Issue]:
     return issues
 
 
-async def _check_layer_color(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_layer_color(backend: AutoCADBackend) -> list[Issue]:
     """Engineering-standard layers must keep their canonical ACI color."""
     issues: list[Issue] = []
     try:
@@ -93,7 +93,7 @@ async def _check_layer_color(backend: "AutoCADBackend") -> list[Issue]:
     return issues
 
 
-async def _check_construction_left(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_construction_left(backend: AutoCADBackend) -> list[Issue]:
     """CONSTRUCTION layer must be empty before drawing_finalize."""
     try:
         ents = await backend.entity_list(layer_filter="CONSTRUCTION", limit=5000)
@@ -113,7 +113,7 @@ async def _check_construction_left(backend: "AutoCADBackend") -> list[Issue]:
     )]
 
 
-async def _check_untrimmed_corner(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_untrimmed_corner(backend: AutoCADBackend) -> list[Issue]:
     """Two LINE endpoints within `tol` but not exactly equal usually means a
     corner where one line overshoots — TRIM/EXTEND/FILLET was forgotten."""
     tol = 0.5  # mm — generous; tighten via PlanSpec.notes later
@@ -156,7 +156,7 @@ async def _check_untrimmed_corner(backend: "AutoCADBackend") -> list[Issue]:
     return issues
 
 
-async def _check_duplicate_entities(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_duplicate_entities(backend: AutoCADBackend) -> list[Issue]:
     """Two LINEs with identical endpoints (in either direction) are duplicates."""
     try:
         lines = await backend.entity_list(type_filter="LINE", limit=5000)
@@ -185,7 +185,7 @@ async def _check_duplicate_entities(backend: "AutoCADBackend") -> list[Issue]:
     return issues
 
 
-async def _check_dim_overlap(backend: "AutoCADBackend") -> list[Issue]:
+async def _check_dim_overlap(backend: AutoCADBackend) -> list[Issue]:
     """Two dimensions whose insertion points are within `tol` likely overlap."""
     tol = 5.0  # mm
     try:
@@ -232,7 +232,7 @@ _FOCUS_DISPATCH = {
 
 
 async def run_critique(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     focus: list[CritiqueFocus] | None = None,
 ) -> list[Issue]:
     """Dispatch each requested focus check and return aggregated issues."""

engineering/gear.py

@@ -71,58 +71,6 @@ def _arc_points(
     return pts
 
 
-def generate_tooth_profile(
-    module: float,
-    teeth: int,
-    pressure_angle: float = 20.0,
-    n_points_per_flank: int = 40,
-) -> list[tuple[float, float]]:
-    """Single tooth profile: right flank, tip arc, mirrored left flank."""
-    pa = math.radians(pressure_angle)
-    pitch_r = module * teeth / 2.0
-    base_r = pitch_r * math.cos(pa)
-    outer_r = pitch_r + module
-    root_r = pitch_r - 1.25 * module
-
-    # Tooth half-thickness angle on the pitch circle.
-    s = math.pi * module / 2.0
-    theta_pitch = s / pitch_r / 2.0
-
-    # Find involute parameter at pitch circle so we can shift the flank to be
-    # symmetric about the tooth centerline (y=0 axis after rotation).
-    if outer_r > base_r:
-        t_pitch = math.sqrt((pitch_r / base_r) ** 2 - 1.0) if pitch_r > base_r else 0.0
-    else:
-        t_pitch = 0.0
-    inv_pitch = math.tan(pa) - pa  # involute function at pressure angle
-    # The flank generated by `generate_involute_flank` starts at theta=0 on the
-    # base circle. The involute point at the pitch radius makes angle inv_pitch
-    # (approx). We rotate the flank by -inv_pitch + theta_pitch so the pitch
-    # crossing sits at +theta_pitch above the tooth-center axis.
-    rot = -inv_pitch + theta_pitch
-
-    right_flank = generate_involute_flank(base_r, root_r, outer_r, n_points_per_flank)
-    right_flank = _rotate_points(right_flank, rot)
-
-    # Left flank by mirroring across the X axis (tooth centerline).
-    left_flank = [(x, -y) for x, y in right_flank]
-
-    # Tip arc connects the outermost right-flank point to the outermost left-flank point.
-    tip_right = right_flank[-1]
-    tip_left = left_flank[-1]
-    a_right = math.atan2(tip_right[1], tip_right[0])
-    a_left = math.atan2(tip_left[1], tip_left[0])
-    if a_left > a_right:
-        a_left -= 2 * math.pi
-    tip_arc = _arc_points(0.0, 0.0, outer_r, a_right, a_left, n=5)
-
-    profile: list[tuple[float, float]] = []
-    profile.extend(right_flank)
-    profile.extend(tip_arc[1:-1])
-    profile.extend(reversed(left_flank))
-    return profile
-
-
 def generate_full_gear_outline(
     module: float,
     teeth: int,
@@ -200,7 +148,7 @@ def generate_full_gear_outline(
 
 
 async def _draw_helix_symbol(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     cx: float,
     cy: float,
@@ -237,7 +185,7 @@ async def _draw_helix_symbol(
 
 
 async def draw_helical_gear_front_view(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     module: float,
     teeth: int,
@@ -330,7 +278,7 @@ async def draw_helical_gear_front_view(
 
 
 async def draw_spur_gear_front_view(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     module: float,
     teeth: int,
@@ -356,7 +304,7 @@ async def draw_spur_gear_front_view(
 
 
 async def draw_gear_section_aa(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     gear_metadata: dict,
     x_offset: float,

engineering/keyway.py

@@ -56,7 +56,7 @@ def keyway_dimensions(bore_diameter: float) -> dict:
 
 
 async def draw_keyed_bore(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     center: tuple[float, float],
     bore_diameter: float,
@@ -110,7 +110,7 @@ async def draw_keyed_bore(
 
 
 async def draw_keyway_section(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     center: tuple[float, float],
     bore_diameter: float,

engineering/layers.py

@@ -71,7 +71,7 @@ LAYER_SET_REGISTRY: dict[str, list[tuple[str, int, str, float, str]]] = {
 STANDARD_LINETYPES: list[str] = ["CENTER", "HIDDEN", "PHANTOM", "DASHED", "DASHDOT"]
 
 
-async def ensure_standard_linetypes(backend: "AutoCADBackend") -> dict[str, str]:
+async def ensure_standard_linetypes(backend: AutoCADBackend) -> dict[str, str]:
     """Idempotently load STANDARD_LINETYPES via backend.linetype_load."""
     try:
         existing = {ln.lower() for ln in await backend.linetype_list()}
@@ -92,13 +92,13 @@ async def ensure_standard_linetypes(backend: "AutoCADBackend") -> dict[str, str]
     return results
 
 
-async def ensure_engineering_layers(backend: "AutoCADBackend") -> dict[str, str]:
+async def ensure_engineering_layers(backend: AutoCADBackend) -> dict[str, str]:
     """Idempotently create every layer in ENGINEERING_LAYERS via backend.layer_create."""
     return await apply_layer_set(backend, "mech")
 
 
 async def apply_layer_set(
-    backend: "AutoCADBackend", standard: str = "mech",
+    backend: AutoCADBackend, standard: str = "mech",
 ) -> dict[str, str]:
     """Idempotently apply a named layer set ('mech', 'pid', 'iso13567')."""
     layer_set = LAYER_SET_REGISTRY.get(standard)

engineering/section.py

@@ -1,82 +0,0 @@
-"""Generic cutting-plane and section-hatch helpers."""
-
-from __future__ import annotations
-
-import math
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from backends.base import AutoCADBackend
-
-
-async def cutting_plane_line(
-    backend: "AutoCADBackend",
-    *,
-    p1: tuple[float, float],
-    p2: tuple[float, float],
-    label: str = "A",
-    layer: str = "PHANTOM",
-) -> dict:
-    """Draw a section line, arrowheads at each end, and 'X-X' labels."""
-    x1, y1 = float(p1[0]), float(p1[1])
-    x2, y2 = float(p2[0]), float(p2[1])
-
-    line = await backend.entity_create_line(x1, y1, x2, y2, layer=layer)
-
-    dx, dy = x2 - x1, y2 - y1
-    length = math.hypot(dx, dy) or 1.0
-    ux, uy = dx / length, dy / length
-    nx, ny = -uy, ux
-
-    arrow_len = max(length * 0.05, 4.0)
-    arrow_w = arrow_len * 0.4
-    arrows: list[str] = []
-
-    for tip_x, tip_y, dir_x, dir_y in (
-        (x1, y1, -ux, -uy),
-        (x2, y2, ux, uy),
-    ):
-        bx = tip_x + dir_x * arrow_len
-        by = tip_y + dir_y * arrow_len
-        wing1_x = bx + nx * arrow_w
-        wing1_y = by + ny * arrow_w
-        wing2_x = bx - nx * arrow_w
-        wing2_y = by - ny * arrow_w
-        a1 = await backend.entity_create_line(tip_x, tip_y, wing1_x, wing1_y, layer=layer)
-        a2 = await backend.entity_create_line(tip_x, tip_y, wing2_x, wing2_y, layer=layer)
-        arrows.extend([a1.handle, a2.handle])
-
-    text = f"{label}-{label}"
-    text_h = max(arrow_len, 3.5)
-    offset = arrow_len * 1.5
-    labels: list[str] = []
-    for tip_x, tip_y, dir_x, dir_y in (
-        (x1, y1, -ux, -uy),
-        (x2, y2, ux, uy),
-    ):
-        tx = tip_x + dir_x * offset + nx * offset * 0.5
-        ty = tip_y + dir_y * offset + ny * offset * 0.5
-        t = await backend.entity_create_text(text, tx, ty, height=text_h, layer="TEXT")
-        labels.append(t.handle)
-
-    return {"line": line.handle, "arrows": arrows, "labels": labels}
-
-
-async def apply_section_hatch(
-    backend: "AutoCADBackend",
-    *,
-    boundary_points: list[list[float]],
-    pattern: str = "ANSI31",
-    angle: float = 45.0,
-    scale: float = 1.0,
-    layer: str = "HATCH",
-) -> str:
-    """Wrapper around backend.entity_create_hatch returning the new handle."""
-    info = await backend.entity_create_hatch(
-        pattern=pattern,
-        boundary_points=boundary_points,
-        scale=scale,
-        angle=angle,
-        layer=layer,
-    )
-    return info.handle

engineering/titleblock.py

@@ -55,7 +55,7 @@ class TitleBlockMetadata:
 
 
 async def apply_iso_a3_titleblock(
-    backend: "AutoCADBackend",
+    backend: AutoCADBackend,
     *,
     metadata: TitleBlockMetadata,
     origin: tuple[float, float] = (0.0, 0.0),

engineering/validator.py

@@ -62,7 +62,7 @@ class DrawingValidator:
 
     async def run(
         self,
-        backend: "AutoCADBackend",
+        backend: AutoCADBackend,
         *,
         expected: dict | None = None,
     ) -> ValidationResult: