fix(skills): correct four API claims that make agent code silently wrong

[TMHSDigital]

Closes #353, #355, #388, #390.

Issue	Was	Now
#353 use-foreach-set rule	Listed vertex "normal" and "index" as foreach_set targets; there was also a duplicated foreach_get line	Names writable attributes only. States that read-only ones are a silent no-op, and how to read and write normals. claude/ regenerated: --check is clean, and the change falls outside the generated summary
#355 geometry-nodes-python	GeometryNode.__subclasses__() (returns []; classes are lazy)	dir(bpy.types) filter, with the reason
#388 engine-export-presets	"pass the suffix and let the operator infer"	Always pass export_format. Added export_format="GLB" to every glTF call in snippets/export_preset_{unity,godot,unreal}.py, snippets/gltf_draco_export.py, the pipeline template (×3) and the skill's code blocks
#390 drivers-and-app-handlers save count	Full path as an ID-property key; counted in save_post	Keyed by basename (≤63 chars). Counted in save_pre, so the count is in the file being saved

Evidence

Proven by live run (--factory-startup; binaries report 5.2.1 LTS and 4.5.11 LTS). Each result is identical on both versions unless the table shows two values.

Probe	5.2.1	4.5.11
dir(bpy.types) GeometryNode names (includes SetPosition)	274	223
Save-count example, 165-char path, save_as + save + reopen	{'a_rather_long_production_shot_name_xxx…': 2}, persisted, no KeyError	same
export_format="GLB" → .glb	t_GLB.glb	same
export_format="GLTF_SEPARATE" → .gltf	.gltf + .bin	same
No export_format, .gltf path	t_None.glb (the bug the skill now warns about)	same
vertices.foreach_set("normal", …) changes nothing	True (no-op)	True

By inspection only:

• Snippet line counts are within the limit (Unreal preset 73/75).
• export_format="GLB" matches the operator's existing default for these .glb call sites, so output is unchanged. The pipeline template and the export-preset examples run in CI smoke.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 143 passed, 1 skipped, 0 failed;142 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;136 passed, 6 skipped, 0 failed;