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/smoke-docs.mjs

@@ -1,4 +1,4 @@
-import { requireToolSuccess, runSmoke } from "./mcp-smoke-client.mjs";
+import { requireToolSuccess, runSmoke, textFrom } from "./mcp-smoke-client.mjs";
 
 const live = process.env.CONTEXT_KIT_LIVE_CHECKS === "1";
 const localSourceSmokeUrl = process.env.CONTEXT_KIT_LOCAL_SOURCE_SMOKE_URL;
@@ -12,7 +12,8 @@ runSmoke({
     const toolNames = await client.requireTools(["docs_query", "docs_sources"]);
 
     const sources = requireToolSuccess("docs_sources", await client.callTool("docs_sources"));
-    if (!Array.isArray(sources?.structuredContent?.result)) {
+    const sourcesPayload = sources?.structuredContent || JSON.parse(textFrom(sources) || "null");
+    if (typeof sourcesPayload?.source_count !== "number") {
       const sourcesText = JSON.stringify(sources);
       throw new Error(`docs_sources returned unexpected payload: ${sourcesText.slice(0, 500)}`);
     }