fix(content): port the #297/#298 export contract to template, skill, rule, example

PR #309 fixed the snippets only. The same two defects remained elsewhere:

- templates/ai-asset-pipeline-template/pipeline.py: the Unreal path scaled
  obj.scale x100 but not obj.location, so node translations stayed in meters
  under centimeter geometry (origin_to_base always moves location.z, so every
  LOD was affected). apply_selected_mesh_transforms looped transform_apply per
  object. Both now match snippets/export_preset_unreal.py / _unity.py.
- skills/ai-mesh-cleanup/SKILL.md: apply_object_transform overrode
  selected_objects=[obj] (does not narrow transform_apply) and was called in a
  loop. Now apply_transforms(objs): one call, selected_editable_objects.
- rules/validate-imported-mesh-scale.mdc: the "required pattern" looped
  transform_apply per object, against prefer-data-over-ops-in-loops. Now one
  call over the scaled meshes.
- examples/export-preset-axis: per-object loop with selected_objects=[obj]
  replaced by the snippet body.

Proof (local, .scratch/blender-5.2.1-windows-x64/blender.exe, 5.2.1 LTS):
- pipeline --preset unreal on tests/smoke/make_pipeline_glb.py fixture:
  lod0 node translation before [0, -1, 0] (m), after [0, -100, 0] (cm),
  matching the cm POSITION data.
- export-preset-axis: happy path exit 0 ("export-preset-axis OK");
  falsifier --same-axis still exits 9.
- check_import_export_rules, check_exit_code_readme, build_claude_rules --check pass.

Closes #326

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

Author: TMHSDigital

examples/export-preset-axis/export_preset_axis.py

@@ -303,15 +303,16 @@ def principled(name, color, metallic, roughness):
 
 
 def apply_selected_mesh_transforms():
-    for obj in list(bpy.context.selected_objects):
-        if obj.type != "MESH":
-            continue
-        with bpy.context.temp_override(
-            object=obj, active_object=obj, selected_objects=[obj]
-        ):
-            bpy.ops.object.transform_apply(
-                location=False, rotation=True, scale=True
-            )
+    # Same body as snippets/export_preset_unity.py: one operator call for the
+    # whole selection. transform_apply acts on selected_editable_objects, so
+    # that is the key to override; selected_objects alone does not narrow it.
+    meshes = [o for o in bpy.context.selected_objects if o.type == "MESH"]
+    if not meshes:
+        return
+    with bpy.context.temp_override(
+        object=meshes[0], active_object=meshes[0], selected_editable_objects=meshes
+    ):
+        bpy.ops.object.transform_apply(location=False, rotation=True, scale=True)
 
 
 def export_selected(path, kwargs):

rules/validate-imported-mesh-scale.mdc

@@ -63,17 +63,18 @@ if scene.unit_settings.system not in {"METRIC", "NONE"}:
     scene.unit_settings.system = "METRIC"
 scene.unit_settings.scale_length = 1.0
 
-for obj in bpy.context.selected_objects:
-    if obj.type != "MESH":
-        continue
-    sx, sy, sz = obj.scale
-    if abs(sx - 1.0) > 1e-6 or abs(sy - 1.0) > 1e-6 or abs(sz - 1.0) > 1e-6:
-        with bpy.context.temp_override(
-            object=obj, active_object=obj, selected_editable_objects=[obj]
-        ):
-            bpy.ops.object.transform_apply(
-                location=False, rotation=True, scale=True
-            )
+def scaled(obj):
+    return any(abs(s - 1.0) > 1e-6 for s in obj.scale)
+
+# One transform_apply for every scaled mesh, not one call per object.
+# transform_apply acts on selected_editable_objects, so that is the key to
+# override; selected_objects alone does not narrow it.
+meshes = [o for o in bpy.context.selected_objects if o.type == "MESH" and scaled(o)]
+if meshes:
+    with bpy.context.temp_override(
+        object=meshes[0], active_object=meshes[0], selected_editable_objects=meshes
+    ):
+        bpy.ops.object.transform_apply(location=False, rotation=True, scale=True)
 ```
 
 For FBX, pass `global_scale=1.0` on import as well, then still check

skills/ai-mesh-cleanup/SKILL.md

@@ -46,11 +46,16 @@ def scale_is_identity(obj, tol=1e-6):
     return abs(sx - 1.0) < tol and abs(sy - 1.0) < tol and abs(sz - 1.0) < tol
 
 
-def apply_object_transform(obj):
+def apply_transforms(objs):
+    # One operator call for the whole list. transform_apply acts on
+    # selected_editable_objects, so that is the key to override; overriding
+    # selected_objects alone does not narrow it.
+    if not objs:
+        return
     with bpy.context.temp_override(
-        object=obj,
-        active_object=obj,
-        selected_objects=[obj],
+        object=objs[0],
+        active_object=objs[0],
+        selected_editable_objects=list(objs),
     ):
         bpy.ops.object.transform_apply(location=False, rotation=True, scale=True)
 
@@ -107,9 +112,7 @@ if not scene_units_are_meters(scene):
     scene.unit_settings.system = "METRIC"
     scene.unit_settings.scale_length = 1.0
 
-for obj in imported_meshes():
-    if not scale_is_identity(obj):
-        apply_object_transform(obj)
+apply_transforms([o for o in imported_meshes() if not scale_is_identity(o)])
 ```
 
 `export_apply=True` on glTF applies **modifiers**, not object scale. Unapplied object scale lands on the glTF node. Witness: `examples/unapplied-scale-gltf/`.

templates/ai-asset-pipeline-template/pipeline.py

@@ -236,11 +236,16 @@ def box_collider(obj, name=None):
 
 
 def apply_selected_mesh_transforms():
-    # Duplicated from snippets/export_preset_unity.py
-    for obj in list(bpy.context.selected_objects):
-        if obj.type != "MESH":
-            continue
-        apply_object_transform(obj)
+    # Duplicated from snippets/export_preset_unity.py. One operator call for
+    # the whole selection; transform_apply reads selected_editable_objects,
+    # so that is the key to override (selected_objects alone does not narrow it).
+    meshes = [o for o in bpy.context.selected_objects if o.type == "MESH"]
+    if not meshes:
+        return
+    with bpy.context.temp_override(
+        object=meshes[0], active_object=meshes[0], selected_editable_objects=meshes
+    ):
+        bpy.ops.object.transform_apply(location=False, rotation=True, scale=True)
 
 
 def select_only(obj):
@@ -272,9 +277,17 @@ def export_preset(filepath, preset, draco):
             export_animations=False,
         )
         return
+    # Unreal: centimeters. Scale location with scale (as in
+    # snippets/export_preset_unreal.py) so node translations are in cm too;
+    # origin_to_base() leaves location.z off zero, so this always matters.
     for obj in list(bpy.context.selected_objects):
         if obj.type != "MESH":
             continue
+        obj.location = (
+            obj.location[0] * 100.0,
+            obj.location[1] * 100.0,
+            obj.location[2] * 100.0,
+        )
         obj.scale = (
             obj.scale[0] * 100.0,
             obj.scale[1] * 100.0,