release: v1.5.0 — discovery layer, honesty debt closed, Wave A

Tool count 131 -> 154; 474 -> 1242 collected tests.

The release exists for two measured reasons. A 149-tool catalog costs a client
~40,300 tokens before it has asked for anything, and a drafter searching the way
drafters think -- FILLET, BPOLY, QSELECT, WBLOCK -- scored df=0 against the stock
index, because those words were simply not in the data.

Discovery and batching
- DISCOVERY_MODE=search replaces the catalog with search_tools + call_tool,
  ranked over an AutoCAD command and synonym corpus (discovery/aliases.py) on
  top of fastmcp's BM25 index. Measured: 40,305 -> 356 tokens advertised.
- cad_batch runs a step list in one round trip; fields= projects result-heavy
  responses. The `core` profile is gone -- discovery replaced it.

Honesty debt (Tier 0)
- OCS/ECS: `extrusion` appeared nowhere in this codebase, so mirrored and
  rotated geometry reported coordinates that were quietly wrong. backends/ocs.py
  translates at the backend boundary; every tool coordinate is WCS on both
  engines, and a tilted plane refuses rather than answering with a number that
  looks fine.
- drawing_save_as(fmt="dwg") wrote DXF bytes to a .dwg path. drawing_audit never
  repaired. analysis_measure_area shoelaced points the caller typed in.
- ezdxf calls gained a per-call timeout, so one hung call can no longer wedge a
  server whose document lock is a single asyncio.Lock.

Architecture
- The 1854-line backend ABC is 19 contract modules; @capability(key, reason=)
  makes optional methods declarative and a gate fails on undeclared holes.
- 8 layout/viewport tools, CHSPACE, CAD_PROGID escape hatch.
- Wave A: selection filters, boundary tracing, hatch depth, annotation objects,
  measurement -- 13 tools of a planned 39. The REGION and 2D-boolean family was
  cut on evidence: add_region() yields zero ACIS bytes and the greiner_hormann
  substitute loses 28.2% of the area on a square with one semicircular edge.

Verified against a live AutoCAD 2026, which found four COM defects no amount of
reading would have caught -- AcadPViewport has no ViewCenter, and the line that
set it had been swallowed by a bare except since v1.4.

Benchmark v3 (15 tasks) and what it caught
- v2 scored this server 10/10, which carried no information: every task in it
  exercised something the server was built around. Five tasks were added because
  they can fail, and three did while being written -- a hatch could not be
  measured though the refusal listed HATCH as measurable, the boundary tools and
  the measure tool disagreed about the same shape (139.2177 vs 139.2699), and a
  circle stored as two bulged vertices measured 0.0.
- Competitor reports are NOT re-scored. They are pinned v1.4 runs against v2 and
  were never asked these five questions; the chart shows those rows `not run`.
- Correctness A/B: 21/24 -> 24/24, zero regressions.

Performance, stated plainly
The published v1.4 perf report was recorded on CPython 3.14 and the new one on
3.11.15, so the apparent 2-6x speedup is the interpreter, not this release.
Re-measured on one interpreter, v1.5.0 is 28% slower creating entities and 22%
slower on the 10k roundtrip. Fully attributed: EZDXF_CALL_TIMEOUT=0 restores
v1.4.0's exact numbers. That is the deadlock fix being paid for, the knob is
documented, and winning it back is on the 1.6 roadmap.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backends/ocs.py

@@ -0,0 +1,100 @@
+"""OCS (Object Coordinate System) to WCS translation, shared by both backends.
+
+DXF does not store 2D geometry in world coordinates. CIRCLE, ARC, LWPOLYLINE,
+TEXT, INSERT and a dimension's text position live in a per-entity frame derived
+from the entity's ``extrusion`` vector by the Arbitrary Axis Algorithm. Mirroring
+flips extrusion to ``(0, 0, -1)`` and leaves the stored x *unnegated*, so a raw
+``dxf.center`` read reports a point the entity is not at — by 60 mm in the
+measured case, while the same response's bounding box (which ezdxf computes
+through the renderer, in WCS) said otherwise.
+
+The rule this module exists to enforce: **everything crossing the MCP boundary is
+WCS.** OCS never leaves the backends.
+
+Both engines share this. ``ezdxf`` is a core dependency, not an extra, so the COM
+backend may import it too — and should, rather than hand-rolling the Arbitrary
+Axis Algorithm a second time. The functions take a raw extrusion/normal triple
+rather than an entity, because a COM object exposes ``.Normal`` where an ezdxf
+one exposes ``.dxf.extrusion``.
+
+Not every entity that *carries* extrusion is affected: ezdxf makes ``ocs()`` a
+pass-through for LINE, MTEXT, ELLIPSE, SPLINE and POINT, which are WCS-native.
+Keying any fix off "has an extrusion attribute" breaks those.
+"""
+
+from __future__ import annotations
+
+import math
+
+from ezdxf.math import OCS, Vec3
+
+_IDENTITY = (0.0, 0.0, 1.0)
+
+
+def is_wcs_frame(extrusion) -> bool:
+    """True when the entity's frame is the identity — nothing to translate."""
+    try:
+        return OCS(Vec3(extrusion)).uz.isclose(_IDENTITY)
+    except Exception:
+        return True  # an unreadable extrusion is not evidence of a rotated frame
+
+
+def is_flat_frame(extrusion) -> bool:
+    """True when the entity's plane is parallel to WCS XY (extrusion is +/-Z).
+
+    Only these frames admit an exact 2D write: given a tilted plane, an ``(x, y)``
+    pair does not determine a point in it, so writing one would displace the
+    entity out of its own plane by an amount nobody supplied.
+    """
+    try:
+        uz = OCS(Vec3(extrusion)).uz
+    except Exception:
+        return True
+    return abs(uz.x) < 1e-12 and abs(uz.y) < 1e-12
+
+
+def to_wcs_2d(extrusion, x, y, z=0.0) -> list[float]:
+    """OCS ``(x, y, z)`` to WCS ``[x, y]``.
+
+    ``z`` is ``dxf.elevation`` for an LWPOLYLINE (whose vertices carry no z of
+    their own) and the point's own z otherwise.
+    """
+    v = OCS(Vec3(extrusion)).to_wcs(Vec3(float(x), float(y), float(z)))
+    return [float(v.x), float(v.y)]
+
+
+def from_wcs(extrusion, x, y, z=0.0) -> tuple[float, float, float]:
+    """WCS ``(x, y, z)`` to OCS ``(x, y, z)`` — the inverse of :func:`to_wcs_2d`.
+
+    Needed on every write path. The read and write halves used to be *equally*
+    wrong, which made a read-then-write round trip an accidental no-op; fixing
+    reads alone would have converted that no-op into a real move.
+    """
+    v = OCS(Vec3(extrusion)).from_wcs(Vec3(float(x), float(y), float(z)))
+    return (float(v.x), float(v.y), float(v.z))
+
+
+def wcs_arc_angles(extrusion, center_ocs, radius, start_deg, end_deg) -> tuple[float, float]:
+    """OCS sweep angles to CCW-in-WCS angles about the WCS centre.
+
+    Computed by mapping the two endpoints through the frame rather than by
+    arithmetic on the angles, so it stays right for any frame. A left-handed
+    frame (``uz.z < 0``, which is what a mirror produces) reverses the direction
+    of the sweep, so the endpoints swap roles.
+    """
+    ocs = OCS(Vec3(extrusion))
+    c0 = Vec3(center_ocs)
+    centre = ocs.to_wcs(c0)
+    angles = []
+    for angle in (float(start_deg), float(end_deg)):
+        point = ocs.to_wcs(Vec3.from_deg_angle(angle, abs(float(radius))) + c0)
+        angles.append(math.degrees(math.atan2(point.y - centre.y, point.x - centre.x)) % 360.0)
+    if ocs.uz.z < 0:
+        angles.reverse()
+    return angles[0], angles[1]
+
+
+def plane_normal(extrusion) -> list[float]:
+    """The entity's plane normal, for reporting a frame that xy cannot express."""
+    uz = OCS(Vec3(extrusion)).uz
+    return [float(uz.x), float(uz.y), float(uz.z)]