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

discovery/aliases.py

@@ -76,6 +76,8 @@ class ToolAliases:
 #       (page_setup_list vs page_setup_apply).
 #   PLOT -- one sheet to PDF (drawing_export_pdf) or every sheet in one go
 #       (batch_plot); a drafter typing it could mean either.
+#   SAVEAS -- the same command saves a copy (drawing_save_as) or a template
+#       (drawing_template_save, its "Drawing Template" file type).
 #
 # Every other AutoCAD command must map to exactly one tool.
 SHARED_ACAD_COMMANDS: frozenset[str] = frozenset(
@@ -91,6 +93,7 @@ SHARED_ACAD_COMMANDS: frozenset[str] = frozenset(
         "PLINE",
         "PLOT",
         "QSELECT",
+        "SAVEAS",
         "SETVAR",
         "ZOOM",
     }
@@ -1462,6 +1465,16 @@ TOOL_ALIASES: dict[str, ToolAliases] = {
             "dwt list",
         ),
     ),
+    "drawing_template_save": ToolAliases(
+        acad=("SAVEAS",),
+        synonyms=(
+            "save as template",
+            "make a dwt",
+            "template from this drawing",
+            "save as dwt",
+            "reuse this sheet setup",
+        ),
+    ),
     "page_setup_apply": ToolAliases(
         acad=("PAGESETUP",),
         synonyms=(