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>

docker/scripts/install.sh

@@ -332,7 +332,6 @@ SELECTED_VARIANT=$(resolve_variant)
 step "Downloading SurfSense files"
 info "Installation directory: ${INSTALL_DIR}"
 mkdir -p "${INSTALL_DIR}/scripts"
-mkdir -p "${INSTALL_DIR}/searxng"
 mkdir -p "${INSTALL_DIR}/proxy"
 
 FILES=(
@@ -342,8 +341,6 @@ FILES=(
     "docker/proxy/Caddyfile:proxy/Caddyfile"
     "docker/postgresql.conf:postgresql.conf"
     "docker/scripts/migrate-database.sh:scripts/migrate-database.sh"
-    "docker/searxng/settings.yml:searxng/settings.yml"
-    "docker/searxng/limiter.toml:searxng/limiter.toml"
 )
 
 for entry in "${FILES[@]}"; do