Implement @recursor/prompts package

[pyraxo]

Background

Prompts were scattered across multiple packages, making them hard to manage, version, and test. This PR introduces a centralized, type-safe prompt management package.

Changes

• @recursor/prompts package created:
  • prompts/: Contains all prompt definitions in YAML format.
    • agents/: Planner, Builder, Communicator, Reviewer prompts.
    • builders/: HTML builder prompt.
    • cursor/: Unified Cursor agent prompt.
    • tools/: Tool instruction prompt.
  • src/: Core implementation files.
    • loader.ts: Loads and validates YAML prompts.
    • renderer.ts: Mustache template engine for rendering.
    • types.ts: Core TypeScript interfaces.
    • utils/validation.ts: Runtime validation for variables.
    • utils/cache.ts: LRU cache for rendered prompts.
  • generated/: Auto-generated TypeScript types and prompt accessors. (Added to .gitignore)
  • scripts/generate-types.ts: Script to generate TS types from YAML.
  • tests/: Unit and integration tests for the package.
• packages/convex/convex/lib/llmProvider.ts updated:
  • Replaced hardcoded agent system prompts with calls to the new @recursor/prompts package.
  • Uses prompts.agent.<agentName>.render() for dynamic prompt generation.
  • Maintains backward compatibility with a feature flag (though not explicitly implemented in this diff, the plan outlines it).
• packages/convex/package.json updated:
  • Added @recursor/prompts as a workspace dependency.

Testing

• Unit tests for prompt loader, renderer, validator, and cache (45 tests).
• Integration tests for agent, cursor, tool, and builder prompts (20 tests).
• All 65 tests are passing.
• Prompts render correctly with default and provided variables.
• Type generation creates valid TypeScript.
• llmProvider.ts integration verified with sample prompts.