chore: address AI-review nits on _ever_connected fix

Drop the try/except AttributeError guard in the new regression test
now that the slot is always defined, and note in the run() comment
that _ever_connected is set once and never cleared.

tests/tools/test_mcp_tool.py

@@ -1444,15 +1444,11 @@ class TestReconnection:
             if run_count == 1:
                 # Initial connection succeeds and registers tools. Setting
                 # ``_ever_connected`` mirrors what the real ``_run_stdio``
-                # does right after a successful ``_discover_tools()`` call;
-                # guarded because the pre-fix class has no such slot.
+                # does right after a successful ``_discover_tools()`` call.
                 self_srv.session = MagicMock()
                 self_srv._tools = []
                 self_srv._ready.set()
-                try:
-                    self_srv._ever_connected = True
-                except AttributeError:
-                    pass
+                self_srv._ever_connected = True
                 return "reconnect"
             if run_count <= 5:
                 # Four consecutive failures on later reconnect attempts --

tools/mcp_tool.py

@@ -4133,6 +4133,7 @@ class MCPServerTask:
                 # that already registered tools once and then dropped would
                 # otherwise be misclassified as never having connected and
                 # re-enter this initial-connect ladder (#94654).
+                # ``_ever_connected`` itself is set once and never cleared.
                 # (Ported from Kilo Code's MCP resilience fix.)
                 if not self._ever_connected:
                     if failure_class == "permanent":