feat(mech): SECTION 23 completes with centre_marks, section_line, hatch_material

centre_marks draws ISO 128-23 centre marks or full centre lines and reads
each circle's real centre and radius back out of the drawing through
entity_get instead of being told them - a radius restated from memory is
the silent wrong number this repository keeps refusing to ship. A handle
that is not a CIRCLE or ARC, and a circle in a plane tilted out of WCS XY
(which has no radius in this frame), are both refused by handle before
anything is written. The dash proportions are not transcribed here: the
prims are plain lines on CENTER, whose linetype already carries them.

section_line draws the ISO 128-40 cutting-plane line - wide segments at
the ends on GEOMETRY, the thin long-dash-dot middle on CENTER, an arrow at
each end whose head sits on the line end and points the way the section is
viewed, the same letter beyond both arrows - and returns the five-key
plane dict {p1, p2, label, direction, style} that mech_view_add(kind=
"section") consumes, so the label on the plan and the label on the view
are the same string by construction. A viewing direction parallel to the
plane is refused rather than drawn.

hatch_material hatches through standards.materials.hatch_for, so the
ISO 128-50 map and its refusal stay in one place; scale multiplies the
material's own pattern scale and angle replaces its angle. An unknown
material is refused with the list before any entity is written.

DEVIATION - one defect in the plan's own draw_material_hatch, fixed here
with two tests that fail against the plan's code. It called
entity_create_hatch with ROLE_LAYER["hatch"] without creating that layer,
the same omission review found in Task 10's draw_annotation_prims.
MEASURED live on AutoCAD 2026 (probe: GetActiveObject, Documents.Add(),
doc.Close(False) in a finally): on a scratch document whose layer table is
['0'], msp.AddHatch(0, "ANSI31", False) + AppendOuterLoop + Evaluate()
leaves the AcDbHatch in model space, and the very next statement
hatch.Layer = "HATCH" - which is the one line _apply_entity_attrs runs -
raises com_error (-2147352567, ..., 'Key not found', ..., -2145386476);
model space then still reports [('AcDbHatch', '0')] and the layer table is
still ['0'], so the refusal leaves an orphan hatch on layer 0. After
doc.Layers.Add("HATCH") the same assignment succeeds. drawing_open runs no
bootstrap, which is exactly when a cut face has no HATCH layer to land on.
draw_material_hatch now calls ensure_annotation_layers before creating the
hatch and reports layer / layers_created, as draw_annotation_prims does.
The whole task re-measured live afterwards through ComBackend on a fresh
scratch document (layer table ['0']): hatch_material -> {'ok': True,
'handle': '82', 'pattern': 'ANSI31', 'layer': 'HATCH', 'layers_created':
['HATCH']} with the entity read back as HATCH on HATCH; centre_marks on a
live CIRCLE r=12.5 -> sources [{'handle': '84', 'center': [80.0, 0.0],
'radius': 12.5}]; section_line -> 9 entities and the five-key plane; layer
table after ['0', 'CENTER', 'GEOMETRY', 'HATCH', 'TEXT']; document closed.

tests/test_mech_marks.py: 17 passed. Gates: ruff check clean, inventory
regenerated to 209 tools, test_tool_registry (engineering 12 -> 15, total
206 -> 209), test_discovery_aliases, test_tool_inventory,
test_capability_contract and test_release_consistency all pass. Full
suite: 3343 passed, the 6 pre-existing failures verified identical with
this change stashed, and
test_release_consistency.py::test_document_numbers_match_the_tree
deselected as Global Constraints instructs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

README.md

@@ -27,7 +27,7 @@ Live through COM on Windows, or headless through ezdxf anywhere — one typed co
 
 </div>
 
-> **v1.5 release snapshot:** 206 tools · 8 resources · 5 prompt templates · 3284 collected tests.
+> **v1.5 release snapshot:** 209 tools · 8 resources · 5 prompt templates · 3284 collected tests.
 > 204 is the **registered** count; a default install advertises 199 over `tools/list`,
 > because `ENABLE_3D` is unset. `system_about` is the runtime authority.
 
@@ -117,7 +117,7 @@ Claude Desktop, Cursor, or any stdio MCP host. For HTTP: `autocad-mcp --transpor
 | Quality loop | `drawing_preflight` → `drawing_plan` → `drawing_critique` → `drawing_refine` → `drawing_finalize` (0–100 score) |
 | Delivery | `drawing_deliver`: DXF/PDF/PNG + SHA-256 manifest + reopen-parity checks |
 
-<sub>206 tools in 23 groups; <code>TOOL_PACKS=core</code> hides the nine <code>pid_*</code> tools and the 22 environment tools (<code>TOOL_PACKS=core,settings</code> keeps the latter) from a client that needs neither. Plus 8 resources that cost nothing in the tool budget (<code>autocad://drawing/info</code>, <code>layers</code>, <code>blocks</code>, <code>entities/stats</code>, <code>entities/{layer_name}</code>, <code>system/status</code>, <code>pid/symbols</code>, <code>standards/isa51</code>) and 5 prompt templates.</sub>
+<sub>209 tools in 23 groups; <code>TOOL_PACKS=core</code> hides the nine <code>pid_*</code> tools and the 22 environment tools (<code>TOOL_PACKS=core,settings</code> keeps the latter) from a client that needs neither. Plus 8 resources that cost nothing in the tool budget (<code>autocad://drawing/info</code>, <code>layers</code>, <code>blocks</code>, <code>entities/stats</code>, <code>entities/{layer_name}</code>, <code>system/status</code>, <code>pid/symbols</code>, <code>standards/isa51</code>) and 5 prompt templates.</sub>
 
 **Two rules worth knowing.** Every coordinate in and out of a tool is WCS on both engines — the one exception is TEXT `rotation`, which stays in the entity frame because a mirrored TEXT is mirror-imaged and no scalar angle expresses that. And never read vertices back and shoelace them: that loses **28.2%** of the area on a semicircular edge, silently. `analysis_measure_entity(handle)` reads the real geometry and states its own accuracy.