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/router.ts

@@ -0,0 +1,38 @@
+import { z } from "zod";
+import { publicProcedure, router } from "./trpc";
+import {
+  getDocument,
+  getRelated,
+  hybridSearch,
+  keywordSearch,
+  listDocuments,
+  semanticSearch,
+} from "@mcpedia/core";
+
+export const appRouter = router({
+  search: publicProcedure
+    .input(z.object({ q: z.string(), limit: z.number().int().min(1).max(50).default(20) }))
+    .query(({ input }) => keywordSearch(input.q, input.limit)),
+
+  semanticSearch: publicProcedure
+    .input(z.object({ q: z.string(), limit: z.number().int().min(1).max(50).default(10) }))
+    .query(async ({ input }) => semanticSearch(input.q, input.limit)),
+
+  hybridSearch: publicProcedure
+    .input(z.object({ q: z.string(), limit: z.number().int().min(1).max(50).default(10) }))
+    .query(async ({ input }) => hybridSearch(input.q, input.limit)),
+
+  getDocument: publicProcedure
+    .input(z.object({ slug: z.string() }))
+    .query(async ({ input }) => getDocument(input.slug)),
+
+  listDocuments: publicProcedure
+    .input(z.object({ section: z.string().optional(), status: z.string().optional() }).optional())
+    .query(async ({ input }) => listDocuments(input ?? {})),
+
+  related: publicProcedure
+    .input(z.object({ slug: z.string(), limit: z.number().int().min(1).max(20).default(5) }))
+    .query(async ({ input }) => getRelated(input.slug, input.limit)),
+});
+
+export type AppRouter = typeof appRouter;