test: close critical coverage gaps and harden PR review fixes

Critical bug fixes from PR review agents:
- client.py: eager asyncio.Lock init, Final[frozenset] for _SENSITIVE_KEYS,
  explicit 429 ToolError after retries exhausted, removed lazy _get_client_lock()
  and _RateLimiter._get_lock() patterns
- exceptions.py: use builtin TimeoutError (UP041), explicit handler before broad
  except so asyncio timeouts get descriptive messages
- docker.py: add update_all to DESTRUCTIVE_ACTIONS (was missing), remove dead
  _MUTATION_ACTIONS constant
- manager.py: _cap_log_content returns new dict (immutable), lock write to
  resource_data, clean dead task from active_subscriptions after loop exits
- diagnostics.py: fix inaccurate comment about semicolon injection guard
- health.py: narrow except ValueError in _safe_display_url, fix TODO comment

New test coverage (98 tests added, 529 → 598 passing):
- test_subscription_validation.py: 27 tests for _validate_subscription_query
  (security-critical allow-list, forbidden keyword guards, word-boundary test)
- test_subscription_manager.py: 12 tests for _cap_log_content
  (immutability, truncation, nesting, passthrough)
- test_client.py: +57 tests — _RateLimiter (token math, refill, sleep-on-empty),
  _QueryCache (TTL, invalidation, is_cacheable), 429 retry loop (1/2/3 failures)
- test_health.py: +10 tests for _safe_display_url (credential strip, port,
  path/query removal, malformed IPv6 → <unparseable>)
- test_notifications.py: +7 importance enum and field length validation tests
- test_rclone.py: +7 _validate_config_data security guard tests
- test_storage.py: +15 (tail_lines bounds, format_kb, safe_get)
- test_docker.py: update_all now requires confirm=True + new guard test
- test_destructive_guards.py: update audit to include update_all

Co-authored-by: Claude <noreply@anthropic.com>

tests/test_notifications.py

@@ -151,3 +151,87 @@ class TestNotificationsActions:
         tool_fn = _make_tool()
         with pytest.raises(ToolError, match="boom"):
             await tool_fn(action="overview")
+
+
+class TestNotificationsCreateValidation:
+    """Tests for importance enum and field length validation added in this PR."""
+
+    async def test_invalid_importance_rejected(self, _mock_graphql: AsyncMock) -> None:
+        tool_fn = _make_tool()
+        with pytest.raises(ToolError, match="importance must be one of"):
+            await tool_fn(
+                action="create",
+                title="T",
+                subject="S",
+                description="D",
+                importance="invalid",
+            )
+
+    async def test_info_importance_rejected(self, _mock_graphql: AsyncMock) -> None:
+        """INFO is listed in old docstring examples but rejected by the validator."""
+        tool_fn = _make_tool()
+        with pytest.raises(ToolError, match="importance must be one of"):
+            await tool_fn(
+                action="create",
+                title="T",
+                subject="S",
+                description="D",
+                importance="info",
+            )
+
+    async def test_alert_importance_accepted(self, _mock_graphql: AsyncMock) -> None:
+        _mock_graphql.return_value = {
+            "notifications": {"createNotification": {"id": "n:1", "importance": "ALERT"}}
+        }
+        tool_fn = _make_tool()
+        result = await tool_fn(
+            action="create", title="T", subject="S", description="D", importance="alert"
+        )
+        assert result["success"] is True
+
+    async def test_title_too_long_rejected(self, _mock_graphql: AsyncMock) -> None:
+        tool_fn = _make_tool()
+        with pytest.raises(ToolError, match="title must be at most 200"):
+            await tool_fn(
+                action="create",
+                title="x" * 201,
+                subject="S",
+                description="D",
+                importance="normal",
+            )
+
+    async def test_subject_too_long_rejected(self, _mock_graphql: AsyncMock) -> None:
+        tool_fn = _make_tool()
+        with pytest.raises(ToolError, match="subject must be at most 500"):
+            await tool_fn(
+                action="create",
+                title="T",
+                subject="x" * 501,
+                description="D",
+                importance="normal",
+            )
+
+    async def test_description_too_long_rejected(self, _mock_graphql: AsyncMock) -> None:
+        tool_fn = _make_tool()
+        with pytest.raises(ToolError, match="description must be at most 2000"):
+            await tool_fn(
+                action="create",
+                title="T",
+                subject="S",
+                description="x" * 2001,
+                importance="normal",
+            )
+
+    async def test_title_at_max_accepted(self, _mock_graphql: AsyncMock) -> None:
+        _mock_graphql.return_value = {
+            "notifications": {"createNotification": {"id": "n:1", "importance": "NORMAL"}}
+        }
+        tool_fn = _make_tool()
+        result = await tool_fn(
+            action="create",
+            title="x" * 200,
+            subject="S",
+            description="D",
+            importance="normal",
+        )
+        assert result["success"] is True