feat(task-8): SECTION 25 grid and symbols - arch_grid, arch_symbol

engineering/arch/symbols.py is pure: grid_prims() draws each structural axis on
the grid role - its CENTER linetype comes from the A-GRID-E-N row, no primitive
sets one - with a 5 mm (paper) bubble and its label touching both ends, on the
symbol role so the circle does not print dashed. Numbers run along x and
letters along y (A..Z, AA, ... none skipped) unless labels names them;
positions are sorted, duplicates and label-count mismatches refused by path.

symbol_prims() draws the four plan symbols: the north arrow (a circle, an
arrow turned CCW from +Y, the vocab(lang) north letter upright beyond the tip),
the section mark (the cut line, a labelled bubble past each end and a viewing
arrow at each end, p1/p2 relative to the origin), the level mark (the triangle,
its line and the value formatted +3.00 / ±0.00, with a decimal comma in
Turkish) and the elevation mark (a circle whose pointers are the tangents from
r*sqrt(2) touching it at +/-45 degrees). An unknown kind is refused with the
list, a parameter the kind does not take with the ones it does. Every size is
a declared paper-mm drafting choice times the plot scale, not a standards value.

arch_grid and arch_symbol draw through draw_prims with ARCH_ROLE_LAYER; alias
records (COLUMNGRIDADD, English and Turkish synonyms), a regenerated inventory,
the README snapshot at 233 tools and the branch-local group snapshot
(entity_creation 21) complete the registration.

Beyond the plan: grid_axes refuses a labels value that is not a dict and a
labels.x / labels.y that is not a list (a string was split into one label per
character, a number raised a bare TypeError). No new ActiveX member: a live run
on AutoCAD 2026 (scratch document, closed after) drew the grid and all four
symbols through draw_prims - A-GRID-E-N created with CENTER, bubbles, texts and
symbols on A-SYMB-T-N, the Turkish north letter K and the level "+3,00".

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

engineering/arch/__init__.py

@@ -40,6 +40,15 @@ from .model import (
     wall_from_dict,
     wall_length,
 )
+from .symbols import (
+    SYMBOL_KINDS,
+    draw_grid,
+    draw_symbol,
+    fmt_level,
+    grid_axes,
+    grid_prims,
+    symbol_prims,
+)
 
 __all__ = [
     "APP_ID",
@@ -56,6 +65,7 @@ __all__ = [
     "Opening",
     "Room",
     "SIZE_BASIS",
+    "SYMBOL_KINDS",
     "Stair",
     "WALL_HATCH_TABLE",
     "WALL_MATERIALS",
@@ -64,15 +74,21 @@ __all__ = [
     "block_spec",
     "catalogue",
     "decode",
+    "draw_grid",
+    "draw_symbol",
     "encode",
     "fmt_area_m2",
+    "fmt_level",
     "fmt_number",
     "from_payload",
+    "grid_axes",
+    "grid_prims",
     "insert_item",
     "opening_from_dict",
     "room_from_dict",
     "segment_of",
     "stair_from_dict",
+    "symbol_prims",
     "tag_prefix",
     "to_payload",
     "to_values",