feat(mcpedia): Phase 2 — semantic + hybrid search, tRPC/Hono API

- @mcpedia/embeddings: OpenRouter provider (9router /v1, encoding_format float),
  chunkText + embedChunks; EMBED_DIM=2048
- document_chunks table (real[] embedding) — pgvector NOT available on shared
  imrnes Postgres, so cosine is computed in-app (KB-scale fine); pgvector deferred
- indexer: chunk + embed + upsert per document
- @mcpedia/search: semanticSearch (cosine) + hybridSearch (FTS+cosine RRF)
- apps/api: Hono + tRPC v11 (6 procedures), serve on :4020
- MCP: semantic_search + hybrid_search tools (6 total)
- web: keyword/hybrid toggle; .env.example + README + PHASES updated

apps/mcp/tsconfig.json

@@ -2,6 +2,8 @@
   "extends": "../../tsconfig.base.json",
   "compilerOptions": {
     "paths": {
+      "@mcpedia/db": ["../../packages/db/src/index.ts"],
+      "@mcpedia/db/schema": ["../../packages/db/src/schema.ts"],
       "@mcpedia/*": ["../../packages/*"]
     }
   },