fix(distribution): make the Cursor plugin installable and document the install

[TMHSDigital]

Closes #347.

Problem

A Cursor user who followed the README got the 9 rules and none of the 16 skills. Cursor loads skills only from a skills folder (.cursor/skills/, .agents/skills/, …) or from an installed plugin, so "reference skills by name in chat" did nothing.

The repo's .cursor-plugin/plugin.json couldn't be that plugin either. Cursor's schema (cursor/plugins schemas/plugin.schema.json) sets additionalProperties: false, and the manifest carried four inventory keys (snippets, templates, examples, showcase). Those keys only mirrored the filesystem for this repo's own CI. There was also no marketplace.json, which a repository import needs.

Change

• .cursor-plugin/plugin.json: drops the four inventory keys; skills and rules stay; adds homepage and repository.
• New .cursor-plugin/marketplace.json: one entry, source: "./".
• scripts/build_plugin_dist.py:
  • the slim plugin-dist tree now ships both Cursor manifests;
  • verify() checks every Cursor skills/rules path exists in the dist;
  • the dist README tells Cursor users to clone the branch into ~/.cursor/plugins/local/.
• README Quick start, landing installSteps (site.json), README update/uninstall:
  • the primary path is a local plugin from plugin-dist;
  • teams can import the repo as a team marketplace;
  • per-project copying of skills/* + rules/*.mdc is the fallback;
  • copying only the rules now explicitly "gives you no skills".
• scripts/site/build_site.py: snippet, template and example-total counts come from disk instead of the manifest arrays.
• validate.yml validate-manifest:
  • rejects any key outside Cursor's schema;
  • requires a kebab-case name;
  • keeps the skills/rules and disk two-way check and the VERSION check;
  • checks marketplace.json lists exactly this plugin with allowed keys.
• CLAUDE.md / AGENTS.md / CONTRIBUTING.md: drop the "list it in .cursor-plugin/plugin.json" authoring step for examples and showcase pieces (one less wiring step per new example).
• Unchanged: the release workflow's version-line regex still matches, and marketplace.json has no version field to sync.

Evidence

• jsonschema against Cursor's published schemas:
  • new plugin.json: valid;
  • new marketplace.json: valid;
  • main's plugin.json: invalid, Additional properties are not allowed ('examples', 'showcase', 'snippets', 'templates' were unexpected).
• New Validate step, run locally: passes (Manifest verified at v0.143.6: {'skills': 16, 'rules': 9}). Falsified against main's manifest, it exits 1 with four is not in the Cursor plugin schema errors.
• build_plugin_dist.py --check: 69 files, 0.28 MB ok. test_build_plugin_dist.py passes.
• Landing page before/after: identical counts. The only difference is that the snippet list is now alphabetical: shader-node-group moved one place, because the manifest order wasn't sorted.
• check_counts.py and check_frontmatter.py pass.

Not run: installing into an actual Cursor client (no Cursor on this host, and I didn't want to modify a local Cursor profile). The layout follows Cursor's documented component discovery, and the manifests validate against Cursor's own schemas.

🤖 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;