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/agents/chat/shared/tools/test_web_search.py

@@ -1,93 +0,0 @@
-"""Tests for the shared ``web_search`` tool's citable-result adaptation.
-
-The tool's network path (SearXNG + live connectors) is out of scope here; these
-cover the pure mapping from raw web results to renderable, citable documents and
-the end-to-end registration of ``WEB_RESULT`` ``[n]`` labels.
-"""
-
-from __future__ import annotations
-
-import pytest
-
-from app.agents.chat.multi_agent_chat.shared.citations import (
-    CitationRegistry,
-    CitationSourceType,
-)
-from app.agents.chat.multi_agent_chat.shared.document_render import render_web_results
-from app.agents.chat.shared.tools.web_search import (
-    _to_renderable_web_documents,
-    _web_source_label,
-)
-
-pytestmark = pytest.mark.unit
-
-
-def _raw_result(url: str, title: str, content: str) -> dict:
-    return {
-        "document": {"title": title, "metadata": {"url": url}},
-        "content": content,
-    }
-
-
-def test_web_source_label_strips_scheme_and_www() -> None:
-    assert _web_source_label("https://www.example.com/path") == "Web · example.com"
-    assert _web_source_label("http://news.site.org/a/b") == "Web · news.site.org"
-    assert _web_source_label("") == "Web"
-
-
-def test_adapter_maps_each_result_to_one_web_passage() -> None:
-    docs = _to_renderable_web_documents(
-        [
-            _raw_result("https://a.com/x", "Alpha", "alpha body"),
-            _raw_result("https://b.com/y", "Beta", "beta body"),
-        ]
-    )
-
-    assert [d.title for d in docs] == ["Alpha", "Beta"]
-    passages = [p for d in docs for p in d.passages]
-    assert all(p.source_type is CitationSourceType.WEB_RESULT for p in passages)
-    assert passages[0].locator == {"url": "https://a.com/x"}
-    assert passages[0].content == "alpha body"
-
-
-def test_adapter_skips_results_without_url_or_content() -> None:
-    docs = _to_renderable_web_documents(
-        [
-            _raw_result("", "No URL", "has content"),
-            _raw_result("https://c.com/z", "Empty", "   "),
-            _raw_result("https://d.com/w", "Good", "real content"),
-        ]
-    )
-
-    assert [d.title for d in docs] == ["Good"]
-
-
-def test_adapter_truncates_on_char_budget() -> None:
-    big = "x" * 30
-    docs = _to_renderable_web_documents(
-        [
-            _raw_result("https://a.com", "A", big),
-            _raw_result("https://b.com", "B", big),
-            _raw_result("https://c.com", "C", big),
-        ],
-        max_chars=50,
-    )
-
-    # First fits (30), second crosses 50 and stops the loop.
-    assert [d.title for d in docs] == ["A"]
-
-
-def test_end_to_end_registers_web_results_for_citation() -> None:
-    registry = CitationRegistry()
-    docs = _to_renderable_web_documents(
-        [_raw_result("https://example.com/a", "Example", "the answer is 42")]
-    )
-
-    block = render_web_results(docs, registry)
-
-    assert block is not None
-    assert "[1] the answer is 42" in block
-    entry = registry.resolve(1)
-    assert entry is not None
-    assert entry.source_type is CitationSourceType.WEB_RESULT
-    assert entry.locator == {"url": "https://example.com/a"}