feat(server): tool profiles, paper-space layouts + viewports, ISO 286 fits, opt-in COM 3D solids

- TOOL_PROFILE=lean|core|full applied in the lifespan via server-level enable/disable; system_about reports the active profile; opt-in solid_* tools are hidden while ENABLE_3D=false
- layouts: layout_list/create/set_current + viewport_create (scaled model viewports) on both backends; drawing_export_pdf(layout=...); ezdxf uses TILEMODE + active-layout binding, COM switches ActiveLayout and restores it
- ISO 286: engineering/fits.py authored IT4-11 + fundamental-deviation tables (1-500 mm; shafts d..p/h/js, holes D..H/JS) with clear out-of-scope errors; dimension_linear/radius/diameter gained fit= resolved from the measured nominal
- tolerances: DIMTM now signed in deviation/limit modes so double-positive fits (p6 +0.035/+0.022) render correctly; legacy positive-magnitude contract preserved
- solids: solid_box/cylinder/extrude/revolve/boolean native on COM (AddBox/AddCylinder/AddRegion+AddExtrudedSolid/AddRevolvedSolid/Boolean); ezdxf reports the honest solid_3d capability boundary
- capability maps: paper_space native, new viewport_render feature, ENABLE_3D-gated solid_3d
- 60 new tests (profiles, layouts, viewports, layout PDF, fits, gating); version pins in tests now read version.__version__

Co-authored-by: Cursor <cursoragent@cursor.com>

config.py

@@ -43,5 +43,16 @@ class Settings:
         )
         self.mcp_auth_token: str = os.environ.get("MCP_AUTH_TOKEN", "").strip()
 
+        # Exposed tool profile: "full" (default, everything), "core" (hides the
+        # raw escape hatches and long-tail tools) or "lean" (a curated ~46-tool
+        # drafting/inspection core for clients with tight tool caps). Invalid
+        # values fall back to "full" with a warning at startup.
+        self.tool_profile: str = os.environ.get("TOOL_PROFILE", "full").lower().strip()
+
+        # Opt-in 3D solids (COM backend only). Disabled by default because the
+        # headless backend cannot produce ACIS solids and live 3D modifies real
+        # documents; enable deliberately.
+        self.enable_3d: bool = os.environ.get("ENABLE_3D", "false").lower().strip() == "true"
+
 
 settings = Settings()