Remove references to deleted docs/ai/ files, update stale comments about
protectedClientIds and pruning-aware comparison to reflect current REPLACE
semantics, fix MAX=30→20 heading, client_0..29→19 comment, use ?? over ||,
preserve lastSeq in server clean-slate path to prevent sequence reuse, and
add clarifying comments for mock limitations and validation guards.
- Add @super-productivity/plugin-api package with TypeScript definitions
- Define core plugin interfaces, types, and manifest structure
- Add plugin hooks system for event-driven architecture
- Create plugin API type definitions and constants
- Add documentation and development guidelines
