docs: structured marketplace descriptions with USER LEVEL, PROJECT LEVEL, and BEST SUITED FOR

[TroonCataroon]

Summary

• Adds marketplaceDetail object to plugin.schema.json with structured fields: summary, userLevel, projectLevel, and bestSuitedFor
• Rewrites marketplace descriptions for all 7 existing plugins (teaching, continual-learning, cursor-team-kit, create-plugin, ralph-loop, agent-compatibility, cli-for-agent) using the new format
• Adds new Appwrite plugin with MCP server (uvx mcp-server-appwrite), skill, and README
• Adds scripts/compose-marketplace-descriptions.mjs to auto-compose description from marketplaceDetail fields
• Adds scripts/sync-plugin-cache.mjs and scripts/run-after-cursor-update.mjs to push composed manifests into the local Cursor plugin cache after updates
• Adds scripts/install-git-post-merge-hook.ps1 for automatic cache sync on git pull
• Updates README with new plugin table and workflow docs
• Adds package.json with ajv/ajv-formats devDependencies for schema validation

Description format

Each plugin description now follows this structure in the marketplace UI:

USER LEVEL: How this helps you as an individual...
PROJECT LEVEL: How this helps your codebase or team...
[Summary sentence]
BEST SUITED FOR: bullet - bullet - bullet

The structured marketplaceDetail fields in plugin.json are the source of truth; npm run compose merges them into the flat description string that the marketplace renders.

Test plan

• npm run validate passes (schema + cross-reference checks)
• npm run compose regenerates all descriptions correctly
• Verify marketplace UI renders updated descriptions after registry ingestion