feat(gateway): C8 PM-decision gate windowed satisfaction

_check_pm_decision_required now requires the latest journal:decision
within pm_decision_window_seconds (default 300). Older decisions no
longer satisfy the gate. Adds JournalService.latest_decision_at.

Future-tighten (out of scope): per-verb-group consumption tracking
would need persistent state — Choreographer is per-request today.

tests/unit/mcp_servers/test_circuit_incomplete_input.py

@@ -36,9 +36,7 @@ _MINIMAL_MANIFEST = {
 
 
 @pytest.fixture()
-def flow_module(
-    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
-) -> types.ModuleType:
+def flow_module(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> types.ModuleType:
     """Import flow_server with minimal env vars needed for constant inspection."""
     manifest_path = tmp_path / "tool-manifest.json"
     manifest_path.write_text(json.dumps(_MINIMAL_MANIFEST))