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/lib/posthog/events.ts

@@ -200,14 +200,12 @@ export function trackAnonymousChatMessageSent(options: {
 	modelSlug: string;
 	messageLength?: number;
 	hasUploadedDoc?: boolean;
-	webSearchEnabled?: boolean;
 	surface?: "free_chat_page" | "free_model_page";
 }) {
 	safeCapture("anonymous_chat_message_sent", {
 		model_slug: options.modelSlug,
 		message_length: options.messageLength,
 		has_uploaded_doc: options.hasUploadedDoc ?? false,
-		web_search_enabled: options.webSearchEnabled,
 		surface: options.surface,
 	});
 }