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>

engineering/tolerances.py

@@ -50,12 +50,17 @@ def build_dim_override(
     elif mode == "deviation":
         if tol_upper is None or tol_lower is None:
             raise ValueError("tol_mode='deviation' requires tol_upper and tol_lower.")
+        # DIMTM convention: the displayed lower deviation is -DIMTM. Callers
+        # pass tol_lower as the magnitude of the minus deviation (0.01 means
+        # -0.01, legacy contract); a *negative* tol_lower expresses a plus
+        # lower deviation, which double-positive ISO 286 fits (e.g. p6
+        # +0.035/+0.022) require.
         override.update(
             {
                 "dimtol": 1,
                 "dimlim": 0,
                 "dimtp": float(tol_upper),
-                "dimtm": abs(float(tol_lower)),
+                "dimtm": float(tol_lower),
             }
         )
     elif mode == "limit":
@@ -66,7 +71,7 @@ def build_dim_override(
                 "dimlim": 1,
                 "dimtol": 0,
                 "dimtp": float(tol_upper),
-                "dimtm": abs(float(tol_lower)),
+                "dimtm": float(tol_lower),
             }
         )
     elif mode == "basic":