feature: skill <-> example index and a single machine-readable examples manifest with version support #377

Value

The 64 runnable examples are the repo's strongest asset, but the skills barely point to them, so neither agents nor humans find the proof for a given skill.

Evidence

• 10 of 16 skills link no examples/ path.
  • slotted-actions-animation never mentions turntable, even though turntable exists to show the channelbag bridge.
  • headless-batch-scripting never mentions temp-override-join.
  • geometry-nodes-python names 2 of its 7 GN examples.
• An agent has to join three overlapping manifests: examples/gallery.json (56 entries), tests/smoke/catalog.json (142 rows, with names like vse-cut-list-pixels ≠ vse-cut-list), and .cursor-plugin/plugin.json.
• Catalog min_version exists on only a few rows, and gallery detail pages show no supported-version range.

Suggested approach

• Add a skills: [...] field per example.
• Generate examples/index.json with name, path, skills, min_version, render/check-only, try-it command, every falsifier flag with its expected exit, and the exit-code table.
• Generate a "Runnable examples" section into each SKILL.md from the index, and fail validation when a skill has none.
• Render 4.5 / 5.1 / 5.2 badges and a "falsify it" copy line on gallery detail pages.

Done when

Every skill links its examples automatically, and one JSON file describes all examples.