feat(task-9): SECTION 22 - std_part_list, std_part_insert, std_feature_draw

engineering/mech/stdparts.py turns the Task 8 tables into real blocks. catalogue()
searches 83 transcribed parts by designation, standard, size or family;
block_spec() emits the typed primitives and DESIG/STD/SIZE/MAT ATTDEFs
block_define takes, in side/top for fasteners and ISO 8826-1 simplified /
ISO 8826-2 detailed for bearings; insert_std_part() defines the block once,
inserts it and writes the std_part ACADMCP_MECH payload the skeleton pins, so
the parts list is a read of the drawing rather than a naming convention.
Threads follow ISO 6410 - minor at 0.8 x major, a thread-length limit line to
the major, a three-quarter minor arc in the end view.

std_feature_draw() adds a thread, a DIN 509 undercut, a DIN 471/472 groove, a
DIN 332 centre hole or an ISO 3601-2 O-ring groove to geometry that already
exists. Its dimensions come from the shared standards registry, never from this
module: an absent table, a size outside coverage or a row missing a dimension is
refused by name, and the DIN 509 relief is drawn from the profile its table
publishes rather than reconstructed here. DIN 332 form R is refused outright.
An unknown designation is refused with the nearest catalogue entries; nothing is
drawn approximately.

SECTION 22 registers the three tools in the new mech pack, with alias records
(INSERT plus shop-floor synonyms in English and Turkish), a regenerated tool
inventory, the README release snapshot at 207 tools in 24 groups, and the frozen
group-size snapshot gaining mech: 3.

Two plan corrections, both verified by running the code:

* the plan's @cad_tool summaries for std_part_insert (118 chars) and
  std_feature_draw (130) overran discovery.serialize.MAX_SUMMARY_CHARS = 110, so
  tests/test_tool_registry.py::test_no_authored_summary_is_long_enough_to_be_truncated
  failed - they would have shipped rendered as "...". Both are shortened to 99
  and 104 characters with the same content.
* the plan's file list omitted tests/test_tool_packs.py, which pins the pack
  registry, the tool_packs report and the group count. It now carries MECH_TOOLS
  and distinguishes ALL_PACKS (declaration order, what "available" reports) from
  ALL_PACKS_ENABLED (sorted, what "enabled" reports) - those two lists stopped
  being the same list when "mech" was appended after "settings".

No new ActiveX member is called: the module drives block_list / block_define /
block_insert / entity_set_xdata / entity_create_* only. The COM path was still
executed live once on AutoCAD 2026 in a scratch document created and closed by
the probe: the bolt block defined with layers CENTER+GEOMETRY, attributes read
back as DESIG/STD/SIZE/MAT = ISO 4014 - M12x60 / ISO 4014 / M12x60 / 8.8, the
ACADMCP_MECH std_part payload round-tripped through entity_get_xdata,
STD_ISO_15_6205_SIMPLIFIED inserted, and the M20 thread's three primitives
landing on GEOMETRY.

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

tests/test_tool_registry.py

@@ -529,6 +529,13 @@ async def test_tool_group_sizes_are_unchanged():
     their secondary tags; those counts returned to their pre-track-E values
     when the section tags landed.) Every other number here has been unchanged
     since the snapshot was taken.
+
+    `mech` appeared (0 -> 3) when v1.6's SECTION 22 opened with the
+    standard-parts catalogue (`std_part_list` / `std_part_insert` /
+    `std_feature_draw`); the `mech` tag is ranked directly after `pid` in
+    `_GROUP_TAG_PRIORITY`, so those tools file under `mech` rather than under
+    their secondary `query` / `create` tags. This snapshot is branch-local:
+    the merge task recomputes it once all four track B+G branches have landed.
     """
     sizes = {label: len(names) for label, names in (await server._tool_groups()).items()}
     assert sizes == {
@@ -545,6 +552,7 @@ async def test_tool_group_sizes_are_unchanged():
         "environment": 22,
         "layers": 14,
         "layouts": 12,
+        "mech": 3,
         "page_setup": 6,
         "pid": 9,
         "premium": 12,
@@ -556,4 +564,4 @@ async def test_tool_group_sizes_are_unchanged():
         "validation": 1,
         "view": 4,
     }
-    assert sum(sizes.values()) == 204
+    assert sum(sizes.values()) == 207