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/docs-rebuild.mjs

@@ -0,0 +1,22 @@
+import { rpc } from "../docker/web-search/mcp-probe.mjs";
+
+const [url, ...sources] = process.argv.slice(2);
+if (!url) throw new Error("usage: node scripts/docs-rebuild.mjs <mcp-url> [source ...]");
+
+await rpc(url, 1, "initialize", {
+  protocolVersion: "2024-11-05",
+  capabilities: {},
+  clientInfo: { name: "context-kit-docs-rebuild", version: "1" }
+}, 10_000);
+const result = await rpc(url, 2, "tools/call", {
+  name: "docs_rebuild",
+  arguments: sources.length ? { sources } : {}
+}, 600_000);
+if (result.isError) {
+  const text = (result.content || []).map(part => part.text || "").join("\n");
+  throw new Error(text || "docs_rebuild failed");
+}
+const structured = result.structuredContent || JSON.parse(
+  (result.content || []).find(part => part.type === "text")?.text || "{}"
+);
+console.log(JSON.stringify(structured, null, 2));