chore: ruff auto-fix PLR6201 — tuple → set in membership tests (#23937)

Replace  with  for all literal-tuple
membership tests. Set lookup is O(1) vs O(n) for tuple — consistent
micro-optimization across the codebase.

608 instances fixed via `ruff --fix --unsafe-fixes`, 0 remaining.
133 files, +626/-626 (net zero).

gateway/status.py

@@ -604,7 +604,7 @@ def acquire_scoped_lock(scope: str, identity: str, metadata: Optional[dict[str,
                             for _line in _proc_status.read_text(encoding="utf-8").splitlines():
                                 if _line.startswith("State:"):
                                     _state = _line.split()[1]
-                                    if _state in ("T", "t"):  # stopped or tracing stop
+                                    if _state in {"T", "t"}:  # stopped or tracing stop
                                         stale = True
                                     break
                     except (OSError, PermissionError):