feat(templates): drawing_template_save on both engines — dwt_write is a declared capability

Live AutoCAD writes a real .dwt through SaveAs(path, ac2018_Template = 66) and
puts the description into the summary Comments; headlessly a .dxf template is
written through drawing_save_as and a .dwt request is refused with capability
dwt_write, naming the DXF route and the COM route. drawing_save_as's "dwt"
entry was 5 (acR13_dxf): a DWT request wrote an R13 DXF under a .dwt name.

Probed live on AutoCAD 2026 (typelib: ac2018_Template = 66, acR13_dxf = 5,
acTemplateDwg absent; the saved file starts AC1032, the document is rebound,
Comments takes). SECTION 19 is now 6 tools; SAVEAS joins SHARED_ACAD_COMMANDS;
templates/README.md documents the two files per template.

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": 171,
+    "tools": 172,
     "resources": 8,
     "prompts": 5,
     "groups": 20
@@ -25,7 +25,7 @@
     "premium": 12,
     "solids": 5,
     "system": 7,
-    "templates": 3,
+    "templates": 4,
     "transactions": 3,
     "validation": 1,
     "view": 4
@@ -741,6 +741,20 @@
         "readOnlyHint": true
       }
     },
+    {
+      "name": "drawing_template_save",
+      "group": "templates",
+      "cost": "mutate",
+      "summary": "Save the current drawing as a template: .dwt on live AutoCAD, .dxf headlessly.",
+      "tags": [
+        "drawing",
+        "template"
+      ],
+      "annotations": {
+        "title": "Save As Template",
+        "destructiveHint": false
+      }
+    },
     {
       "name": "drawing_undo",
       "group": "drawing",