fix(rules): bulk-data and bmesh rules name only attributes that exist and are writable

Verified on .scratch/blender-4.5.11-windows-x64 and blender-5.2.1 (same on both):
MeshLoop.normal is read-only; MeshEdge has no `crease` and no `use_sharp`
(the property is use_edge_sharp); Mesh.vertex_layers_int does not exist;
normals_split_custom_set exists; a crease_edge FLOAT and sharp_edge BOOLEAN
edge attribute take foreach_set("value", ...); mesh.attributes["missing"]
raises KeyError.

- use-foreach-set-for-bulk-data: the flagged-pattern list no longer offers
  `loop.normal = ...` (unwritable); "where else it works" now says read loop
  normals with foreach_get and write custom normals with
  normals_split_custom_set, lists use_edge_sharp, and moves crease to the
  crease_edge attribute; adds generic mesh.attributes[name].data.
- always-free-bmesh: the example exception is mesh.attributes["missing"]
  (KeyError) instead of the removed vertex_layers_int (whose .get() would not
  have raised anyway).

Closes #330

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: TMHSDigital

rules/always-free-bmesh.mdc

@@ -73,8 +73,8 @@ finally:
 
 The `try`/`finally` covers the case where any operation between `bmesh.new()`
 and `bm.free()` raises. Without it, a `KeyError` reading
-`mesh.vertex_layers_int.get("missing")` skips the `free()`, and the BMesh
-leaks for the remaining session.
+`mesh.attributes["missing"]` skips the `free()`, and the BMesh leaks for the
+remaining session.
 
 For the edit-mode case where the bmesh comes from `bmesh.from_edit_mesh()`,
 **do not call `bm.free()`**. Edit-mode bmeshes are owned by Blender and

rules/use-foreach-set-for-bulk-data.mdc

@@ -22,7 +22,7 @@ Any of these patterns:
 
 - `for v in mesh.vertices: v.co = ...`
 - `for i, v in enumerate(mesh.vertices): v.co = coords[i]`
-- `for loop in mesh.loops: loop.normal = ...`
+- `for e in mesh.edges: e.use_seam = ...`
 - `for face in mesh.polygons: face.use_smooth = True`
 - Manual `enumerate` loops that index into a parallel array of values
 
@@ -99,11 +99,17 @@ Pre-allocate the buffer; do not let `foreach_get` allocate per call.
 
 Same pattern applies to:
 
-- `mesh.loops` (per-loop normals, custom split normals, UV coordinates
-  via the UV layer's `data`)
+- `mesh.loops`: `foreach_get("normal", ...)` to read per-loop normals
+  (`MeshLoop.normal` is read-only; write custom normals in bulk with
+  `mesh.normals_split_custom_set(...)` instead), and UV coordinates via the
+  UV layer's `data`
 - `mesh.polygons` (per-face material index, smooth flag, area)
-- `mesh.edges` (per-edge use_seam, use_sharp, crease)
-- `bpy.types.MeshUVLoopLayer.data` and other layer collections
+- `mesh.edges` (per-edge `use_seam`, `use_edge_sharp`). Edge crease is not
+  an edge property on 4.5 LTS or 5.x; it is the `crease_edge` FLOAT
+  attribute: `mesh.attributes["crease_edge"].data.foreach_set("value", buf)`
+  (create it with `mesh.attributes.new("crease_edge", "FLOAT", "EDGE")`).
+- `mesh.attributes[name].data` for any generic attribute (`"value"`,
+  `"vector"` or `"color"` key by type), and `MeshUVLoopLayer.data`
 
 For example, batch-flag every face as smooth-shaded: