fix(#3210 review): convert bare urlopen TimeoutError to ValueError in _joplin_api_get

Codex+Opus pre-release gate both flagged: TimeoutError is now in the
consolidated _CLIENT_DISCONNECT_ERRORS dispatch set, so a bare socket-connect
TimeoutError from Joplins urlopen(timeout=8) — which is NOT always URLError-
wrapped — would escape _handle_notes_search and be swallowed by the dispatch
disconnect handler as a fake client disconnect (silent empty response, no log).
Catch (URLError, TimeoutError) at the route so it surfaces as a clean
"not reachable" ValueError -> JSON error. Adds a regression test.

Co-authored-by: someaka <someaka@users.noreply.github.com>

tests/test_webui_notes_sources.py

@@ -138,6 +138,30 @@ def test_joplin_get_note_validates_id_and_truncates_body(monkeypatch):
     assert "Preview truncated" in note["body"]
 
 
+def test_joplin_api_get_converts_bare_timeout_to_valueerror(monkeypatch):
+    """Regression (#3210 review): a bare socket TimeoutError from urlopen must
+    surface as a ValueError, not propagate.
+
+    `urlopen(timeout=8)` can raise a bare ``TimeoutError`` (not URLError-wrapped)
+    on a slow/unreachable Joplin server. After the consolidated client-disconnect
+    handling landed, ``TimeoutError`` is in the request dispatch's
+    ``_CLIENT_DISCONNECT_ERRORS`` set — so if it escaped ``_joplin_api_get`` it
+    would be swallowed as a fake client disconnect (silent empty response, no
+    log). It must be converted to a "not reachable" ValueError at the route.
+    """
+    import pytest
+    from api import routes
+
+    def fake_urlopen(request, timeout):
+        raise TimeoutError("timed out")
+
+    monkeypatch.setattr(routes, "_joplin_connection_from_config", lambda: ("http://127.0.0.1:41184", "secret-token"))
+    monkeypatch.setattr("urllib.request.urlopen", fake_urlopen)
+
+    with pytest.raises(ValueError, match="not reachable"):
+        routes._joplin_api_get("/search", {"query": "hello world"})
+
+
 def test_joplin_api_get_sends_header_and_query_token_for_clip_search_compat(monkeypatch):
     from api import routes