Overhaul docs retrieval and web search quality

Replace the abandoned llms-txt-mcp/Chroma docs backend with an in-repo
MCP service: SQLite WAL + FTS5 + sentence-transformer embeddings,
transactional source replacement, persisted state across restarts,
singleflight refresh with conditional requests, hybrid lexical/semantic
ranking with exact-duplicate collapse, source/host filters, and
explicit-by-default content retrieval. Add docs_rebuild and a
docs-rebuild CLI command.

Add deterministic llms-full.txt snapshot generation for machine-local
menus with hash-validated provenance manifests; lifecycle commands
promote a local menu to its snapshot only when the manifest validates.
Switch public source profiles to content-bearing llms-full.txt feeds.

Improve web search: bounded provider fallback with per-attempt
diagnostics and cancellation, an optional Brave Search API provider,
strict SearXNG engine selection, capped link/media extraction, and a
real engine=browser renderer that routes every request through the
existing SSRF vetting while blocking WebSockets, non-GET traffic, and
private destinations.

Extend release checks with offline unit suites and isolated candidate
container tests for both images.

scripts/test-docs-candidate.mjs

@@ -0,0 +1,43 @@
+import assert from "node:assert/strict";
+
+import { probeMcp, rpc } from "../docker/web-search/mcp-probe.mjs";
+
+const url = process.argv[2];
+if (!url) throw new Error("usage: node scripts/test-docs-candidate.mjs <mcp-url>");
+
+const required = ["docs_query", "docs_rebuild", "docs_refresh", "docs_sources"];
+const tools = await probeMcp(url, { timeoutMs: 10_000, expectedTools: required });
+assert.deepEqual(tools, required);
+
+function structured(result) {
+  if (result.structuredContent) return result.structuredContent;
+  const text = (result.content || []).find(part => part.type === "text")?.text;
+  return text ? JSON.parse(text) : null;
+}
+
+const refreshed = structured(await rpc(url, 3, "tools/call", {
+  name: "docs_refresh",
+  arguments: { force: true }
+}, 120_000));
+assert.equal(refreshed.sources[0].status, "updated", JSON.stringify(refreshed.sources[0]));
+assert(refreshed.sources[0].document_count >= 2);
+
+const search = structured(await rpc(url, 4, "tools/call", {
+  name: "docs_query",
+  arguments: { query: "CONTEXT_KIT_EXACT_IDENTIFIER_20260724", limit: 3 }
+}, 30_000));
+assert.equal(search.search_results[0].title, "Environment Variables");
+assert.deepEqual(search.retrieved_content, {});
+
+const identifier = search.search_results[0].id;
+const retrieved = structured(await rpc(url, 5, "tools/call", {
+  name: "docs_query",
+  arguments: {
+    query: "CONTEXT_KIT_EXACT_IDENTIFIER_20260724",
+    retrieve_ids: [identifier],
+    max_bytes: 12_000
+  }
+}, 30_000));
+assert(retrieved.retrieved_content[identifier].content.includes("CONTEXT_KIT_EXACT_IDENTIFIER_20260724"));
+
+console.log("pass docs candidate transport, refresh, hybrid search, and explicit retrieval");