feat(templates): five bundled templates built by the server's own tools; drawing_new(template=name)

SECTION 19 grows to five tools with drawing_template_list; drawing_new takes a
bundled name (iso_a3_mech, iso_a1_arch, iso_a3_pid, ansi_b_mech, ansi_d_arch)
or a .dwt/.dxf path and reports template: {name|path, path, source}.

scripts/build_templates.py builds templates/*.dxf through EzdxfBackend
(layer set, header DIM variables until group S's styles land, drawing_settings,
sheet tab, ISO 5457 frame on A3, page_setup_apply) and --check pins them
reproducible. One drift the plan's same-process measurement could not see is
fixed at the source rather than masked: ezdxf orders CLASSES by set iteration,
so two processes disagreed on LAYOUT / ACDBPLACEHOLDER; the section is re-keyed
(required list first, then by name) before the save.

The root .gitignore ignores *.dxf as generated output; templates/*.dxf is
un-ignored there, since the bundled set is the one DXF that is committed.

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

docs/tool-inventory.json

@@ -3,7 +3,7 @@
   "schema_version": 1,
   "package_version": "1.5.1",
   "totals": {
-    "tools": 170,
+    "tools": 171,
     "resources": 8,
     "prompts": 5,
     "groups": 20
@@ -25,7 +25,7 @@
     "premium": 12,
     "solids": 5,
     "system": 7,
-    "templates": 2,
+    "templates": 3,
     "transactions": 3,
     "validation": 1,
     "view": 4
@@ -596,7 +596,7 @@
       "name": "drawing_new",
       "group": "drawing",
       "cost": "mutate",
-      "summary": "Start a blank drawing, pre-seeded with the standard engineering layers.",
+      "summary": "Start a drawing: blank with the engineering layers, or from a bundled/own template.",
       "tags": [
         "drawing"
       ],
@@ -726,6 +726,21 @@
         "destructiveHint": false
       }
     },
+    {
+      "name": "drawing_template_list",
+      "group": "templates",
+      "cost": "read",
+      "summary": "List the five bundled drawing templates: standard, sheet, layers, styles, page setup.",
+      "tags": [
+        "drawing",
+        "query",
+        "template"
+      ],
+      "annotations": {
+        "title": "List Drawing Templates",
+        "readOnlyHint": true
+      }
+    },
     {
       "name": "drawing_undo",
       "group": "drawing",