fix: correct version-accuracy defects across skills and snippets

[TMHSDigital]

Summary

Corrects four confirmed version-accuracy defects in skills/snippets, found in an audit and re-verified empirically on Blender 4.5.10 LTS and 5.1.1 (a fresh 4.5 LTS install — the prior audit only had 4.4.3) plus the 4.4/4.5/5.0 release notes.

No content added or removed — counts unchanged (12 skills, 6 rules, 2 templates, 17 snippets). All snippets/templates py_compile. The three corrected snippets were re-run on both 4.5.10 and 5.1.1 and behave correctly.

Defects fixed

1. EEVEE engine id was inverted (CRITICAL). Correct: BLENDER_EEVEE_NEXT on 4.2–4.5, BLENDER_EEVEE on 5.0+ (5.0 RN: "identifier was changed from BLENDER_EEVEE_NEXT to BLENDER_EEVEE"; introspection: 5.1.1 rejects _NEXT, 4.5.10 rejects plain). Fixed version-branch-skeleton.py, headless-batch-scripting (detect snippet, argparse choices, prose), procedural-materials-and-shaders table.
2. Slotted Actions framing + fabricated 4.5 shim (CRITICAL/MAJOR). Slotted model shipped in 4.4; legacy action.fcurves removed in 5.0; action_ensure_channelbag_for_slot is new in 5.0 and absent on 4.4/4.5 (no shim). Rewrote slotted-actions-animation with a real version-branching helper (ensure-fn on 5.0+, strip.channelbag(slot, ensure=True) on 4.4/4.5), removed the bogus hasattr(action,'slots') "5.x sniff", fixed the compatibility matrix and the snippet header.
3. save_pre handler signature (MAJOR). Arg0 is the file-path string, not a Scene (4.5 docs + introspection on both versions). Fixed the handler table and worked examples in drivers-and-app-handlers and app-handler-registration.py to reach scenes via bpy.data.
4. Geometry Nodes version tags (MAJOR). For Each Element (4.3) and Mesh to SDF Grid (4.3) were mis-tagged "5.0+"; corrected labels and changed has_for_each_element() to >= (4,3,0). NodeSocketBundle/has_bundles kept at 5.0 (verified: interface socket works in 5.1, TypeError in 4.5).

Verification

• python -m py_compile passes on all snippets + templates.
• Edited snippets re-run on 4.5.10 and 5.1.1: EEVEE id resolves & sets per version; save_pre handler clears cache via bpy.data without crashing; cross-version channelbag keyframing works.
• Frontmatter intact, standards-version: 1.10.0 unchanged, README counts unchanged.

Out of scope (flagged, not changed here)

• .cursor-plugin/plugin.json "version": "0.2.3" lags VERSION 0.2.4 — release-doc-sync does not own it, so syncing here would just re-lag after the next bump. Separate meta-repo question.
• Newly observed: the bundle node bl_idnames GeometryNodeCombineBundle/GeometryNodeSeparateBundle in geometry-nodes-python are undefined in 5.1.1 (RuntimeError) though present in 4.5.10 — a latent defect outside this PR's 4 defects; needs the correct 5.x node names determined before fixing.
• Efficacy gap (no headless origin-recenter recipe) → v0.3.0 candidate.

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