feat(agents): consolidate connectors under mcp_discovery; route web search through google_search

MCP consolidation:
- Route all MCP-capable connectors (Slack, Jira, Linear, ClickUp, Airtable,
  Notion, Confluence, interim Gmail/Calendar, custom MCP) through a single
  `mcp_discovery` subagent. Drive/OneDrive/Dropbox stay native to enrich the KB.
- Deprecate Discord/Teams/Luma: no viable official MCP server.

Google-only web search:
- Remove the main-agent `web_search` tool and the SearXNG platform service;
  all public web search now flows through the `google_search` subagent via task().
- Deprecate the Tavily/SearXNG/Linkup/Baidu search connectors (HTTP 410 on
  create, "Deprecated" badge); guide heavy users to the custom MCP connector.
- Remove web search from anonymous chat (pure Q&A).
- Tear SearXNG out of docker compose + install scripts; drop tavily-python
  and linkup-sdk deps and their config/env vars.

Fix:
- metrics._package_version() now swallows any metadata lookup failure. A
  malformed editable-install distribution with no `Version` field raised
  KeyError deep in importlib.metadata, and since it runs on every
  record_subagent_invoke_duration call it was crashing every task()
  delegation. Verified end-to-end against live GPT-5.4.

Co-authored-by: Cursor <cursoragent@cursor.com>

surfsense_web/contexts/anonymous-mode.tsx

@@ -9,8 +9,6 @@ export interface AnonymousModeContextValue {
 	setModelSlug: (slug: string) => void;
 	uploadedDoc: { filename: string; sizeBytes: number } | null;
 	setUploadedDoc: (doc: { filename: string; sizeBytes: number } | null) => void;
-	webSearchEnabled: boolean;
-	setWebSearchEnabled: (enabled: boolean) => void;
 	resetKey: number;
 	resetChat: () => void;
 }
@@ -36,7 +34,6 @@ export function AnonymousModeProvider({
 	const [uploadedDoc, setUploadedDoc] = useState<{ filename: string; sizeBytes: number } | null>(
 		null
 	);
-	const [webSearchEnabled, setWebSearchEnabled] = useState(true);
 	const [resetKey, setResetKey] = useState(0);
 
 	const resetChat = () => setResetKey((k) => k + 1);
@@ -59,12 +56,10 @@ export function AnonymousModeProvider({
 			setModelSlug,
 			uploadedDoc,
 			setUploadedDoc,
-			webSearchEnabled,
-			setWebSearchEnabled,
 			resetKey,
 			resetChat,
 		}),
-		[modelSlug, uploadedDoc, webSearchEnabled, resetKey]
+		[modelSlug, uploadedDoc, resetKey]
 	);
 
 	return <AnonymousModeContext.Provider value={value}>{children}</AnonymousModeContext.Provider>;