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.

docker/web-search/overrides/brave.js

@@ -0,0 +1,42 @@
+import { HTTP_TIMEOUT } from "../constants.js";
+import { searchCache, createCacheKey } from "../utils/cache.js";
+
+export class BraveProvider {
+  name = "brave";
+  configured = Boolean(process.env.BRAVE_SEARCH_API_KEY);
+
+  async search(q, limit, lang, signal) {
+    if (!this.configured) return [];
+    const cacheKey = createCacheKey("brave", q, limit, lang);
+    const cached = searchCache.get(cacheKey);
+    if (cached) return cached;
+    const url = new URL("https://api.search.brave.com/res/v1/web/search");
+    url.searchParams.set("q", q);
+    url.searchParams.set("count", String(Math.min(limit, 20)));
+    url.searchParams.set("search_lang", lang.split(/[-_]/)[0] || "en");
+    const response = await fetch(url, {
+      headers: {
+        Accept: "application/json",
+        "X-Subscription-Token": process.env.BRAVE_SEARCH_API_KEY
+      },
+      signal: signal ? AbortSignal.any([signal, AbortSignal.timeout(HTTP_TIMEOUT)]) : AbortSignal.timeout(HTTP_TIMEOUT)
+    });
+    if (!response.ok) throw new Error(`Brave HTTP ${response.status}`);
+    const data = await response.json();
+    const items = (data.web?.results || []).slice(0, limit).flatMap(result => {
+      if (!result.title || !result.url) return [];
+      return [{
+        title: result.title,
+        url: result.url,
+        snippet: result.description || undefined,
+        source: "brave"
+      }];
+    });
+    searchCache.set(cacheKey, items);
+    return items;
+  }
+
+  async isAvailable() {
+    return this.configured;
+  }
+}