feat(skills): link every skill to the examples that prove it

[TMHSDigital]

Refs #377. This meets the issue's "Done when": every skill links its examples automatically, and one JSON file describes all examples. The gallery version badges and "falsify it" line from the suggested approach are not in this PR, so the issue stays open for them.

What changed

• examples/skills.json (hand-edited): example → skills it proves, for all 64 examples. I mapped them from each README and script. Where a README claimed more than the script does, I checked: e.g. "engine-export-presets" only where the script actually calls an exporter.
  • 52 examples map to at least one skill.
  • 12 cover subjects no skill teaches (grease pencil, compositor, light linking, constraints…) and map to [].
• scripts/build_examples_index.py generates:
  • examples/index.json, one record per example: script, skills, render, min_version, run, summary, every smoke falsifiers entry with its expected exit and version floor, and the README exit_codes table. Summaries come from the gallery teaches line (rendered examples) or the README lead (check-only). They are cut at a sentence end followed by whitespace, so dotted API paths survive (the PR fix: gallery alts truncate on dotted API paths + version example prompt #68 bug), and never inside a code span or parenthesis.
  • A marked "Runnable examples" section in every SKILL.md, placed before "References": absolute link, summary and one falsifier per example. addon-scaffolding, bl-info-migration and ui-panels say none exists yet and link examples: add runnable check-only examples for operators, ui-panels, addon-scaffolding and bl-info-migration #378. Listing a pending skill that has gained an example is an error, so the list shrinks as examples: add runnable check-only examples for operators, ui-panels, addon-scaffolding and bl-info-migration #378 lands.
• --check runs in Validate and tests/run_all.py.
• CLAUDE.md and docs/new-example-prompt.md add the mapping to the example wiring list.

Evidence (local runs)

• build_examples_index.py --check passes.
• check_skill_refs.py: every link is a live absolute link.
• tests/run_all.py: 31 passed, 0 failed.
• Falsifiers:
  • Deleting turntable and adding a bogus ghost-example → no-such-skill gives 4 errors, exit 1: unmapped example, unknown directory, unknown skill, and slotted-actions-animation left without an example.
  • Hand-editing a generated SKILL.md section gives "is stale", exit 1.
• Fixed during the falsifier run: a broken mapping first crashed with a KeyError instead of reporting. It now reports and exits 1.
• With fix(plugin): point skills at the files the plugin installed #439: the plugin dist pins these tree/main/examples/... links to the release tag.

Inspection only: the skill assignments are judgment calls. Reviewers should check examples/skills.json.

🤖 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;162 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;147 passed, 15 skipped, 0 failed;