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/web/app/search/page.tsx

@@ -1,18 +1,45 @@
 import Link from "next/link";
-import { keywordSearch } from "@mcpedia/core";
+import { keywordSearch, hybridSearch } from "@mcpedia/core";
+
+type Mode = "keyword" | "hybrid";
 
 export default async function SearchPage({
   searchParams,
 }: {
-  searchParams: Promise<{ q?: string }>;
+  searchParams: Promise<{ q?: string; mode?: string }>;
 }) {
-  const { q } = await searchParams;
+  const { q, mode } = await searchParams;
   const query = q?.trim() ?? "";
-  const hits = query ? await keywordSearch(query, 30) : [];
+  const activeMode: Mode = mode === "hybrid" ? "hybrid" : "keyword";
+
+  const hits = query
+    ? activeMode === "hybrid"
+      ? await hybridSearch(query, 30)
+      : await keywordSearch(query, 30)
+    : [];
+
+  const toggle = (m: Mode) => `/search?q=${encodeURIComponent(query)}&mode=${m}`;
 
   return (
     <div className="space-y-4">
-      <h1 className="text-2xl font-semibold tracking-tight">Search</h1>
+      <div className="flex items-center justify-between">
+        <h1 className="text-2xl font-semibold tracking-tight">Search</h1>
+        <div className="flex rounded overflow-hidden border border-zinc-300 dark:border-zinc-700 text-sm">
+          <Link
+            href={toggle("keyword")}
+            className={`px-3 py-1.5 ${activeMode === "keyword" ? "bg-zinc-900 text-white dark:bg-zinc-100 dark:text-zinc-900" : "hover:bg-zinc-100 dark:hover:bg-zinc-800"}`}
+          >
+            Keyword
+          </Link>
+          <Link
+            href={toggle("hybrid")}
+            className={`px-3 py-1.5 ${activeMode === "hybrid" ? "bg-zinc-900 text-white dark:bg-zinc-100 dark:text-zinc-900" : "hover:bg-zinc-100 dark:hover:bg-zinc-800"}`}
+          >
+            Hybrid
+          </Link>
+        </div>
+      </div>
+
       <form method="get" className="flex gap-2">
         <input
           name="q"
@@ -20,6 +47,7 @@ export default async function SearchPage({
           placeholder="e.g. websocket contract typescript"
           className="flex-1 rounded border border-zinc-300 dark:border-zinc-700 bg-white dark:bg-zinc-900 px-3 py-2 text-sm"
         />
+        <input type="hidden" name="mode" value={activeMode} />
         <button
           type="submit"
           className="rounded bg-zinc-900 text-white dark:bg-zinc-100 dark:text-zinc-900 px-4 py-2 text-sm font-medium"
@@ -44,6 +72,9 @@ export default async function SearchPage({
             >
               {h.doc.title}
             </Link>
+            {/* Snippet comes from Postgres ts_headline (keyword mode) or our own
+                chunk content (hybrid mode) — both trusted, first-party data, not
+                user input. The only markup is <mark> from ts_headline. */}
             <p
               className="text-sm text-zinc-600 dark:text-zinc-400 mt-1"
               dangerouslySetInnerHTML={{ __html: h.snippet }}