Integrate semantic search with RAG capabilities

[janhesters]

Background

The fan-out search implementation in ai/tools/search/fan-out.js includes a stub for semantic search:

const searchSemantic = async (db, query) => {
  // Stub - returns empty array
  // TODO: Integrate with built-in RAG capabilities
  return [];
};

Requested Feature

Implement semantic search using RAG (Retrieval-Augmented Generation) capabilities to improve search relevance for natural language queries.

Acceptance Criteria

• Integrate with built-in RAG or embedding-based search
• Search should find semantically similar documents even without exact keyword matches
• Results should be weighted appropriately alongside FTS5 and metadata searches
• Add unit tests for semantic search functionality

Related

• Part of the RLM Phase 1 foundation work
• PR Add SQLite-based indexing and search tools (RLM Phase 1) #87 established the search infrastructure