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/api/src/trpc.ts

@@ -0,0 +1,11 @@
+import { initTRPC } from "@trpc/server";
+import { db } from "@mcpedia/db";
+
+export interface Context {
+  db: typeof db;
+}
+
+export const t = initTRPC.context<Context>().create();
+
+export const router = t.router;
+export const publicProcedure = t.procedure;