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_backend/tests/unit/observability/test_otel.py

@@ -166,8 +166,8 @@ class TestMetricHelpers:
             model="gpt-4o",
             provider="openai",
         )
-        metrics.record_tool_call_duration(3.0, tool_name="web_search")
-        metrics.record_tool_call_error(tool_name="web_search")
+        metrics.record_tool_call_duration(3.0, tool_name="scrape_webpage")
+        metrics.record_tool_call_error(tool_name="scrape_webpage")
         metrics.record_kb_search_duration(
             4.0,
             workspace_id=1,
@@ -278,3 +278,30 @@ class TestEnabledIntegration:
             sp.set_attribute("tool.truncated", False)
         with otel.model_call_span(model_id="m", provider="p") as sp:
             sp.set_attribute("retry.count", 3)
+
+
+class TestPackageVersionResilience:
+    """A version-tag lookup must never crash the request path (e.g. subagents).
+
+    An editable/dynamic install can have distribution metadata with no
+    ``Version`` field, which raises ``KeyError`` deep inside importlib.metadata.
+    ``_package_version`` must swallow that and every other lookup failure.
+    """
+
+    def test_missing_version_key_falls_back(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        def _raise_key_error(_name: str) -> str:
+            raise KeyError("Version")
+
+        monkeypatch.setattr(metrics.metadata, "version", _raise_key_error)
+        assert metrics._package_version() == "unknown"
+
+    def test_package_not_found_falls_back(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        def _raise_not_found(_name: str) -> str:
+            raise metrics.metadata.PackageNotFoundError("surf-new-backend")
+
+        monkeypatch.setattr(metrics.metadata, "version", _raise_not_found)
+        assert metrics._package_version() == "unknown"