feat(PMEM-WP-0017): federated store management CLI and activity reports

Add phase_memory.management for cross-store discovery and windowed
activity reporting. Extend the phase-memory CLI with stores list and
report commands, plus make report-7d for the default weekly operator view.

tests/fixtures/management/federated-report-aggregate.json

@@ -0,0 +1,33 @@
+{
+  "aggregate": {
+    "active_store_count": 2,
+    "audit_event_count": 1,
+    "by_operation": {
+      "audit.query": 1
+    },
+    "by_outcome": {
+      "resolved": 1,
+      "skipped": 1,
+      "unknown": 1
+    },
+    "by_session_kind": {
+      "lifecycle.apply": 1,
+      "warden.agent.codex": 1,
+      "warden.operator": 1
+    },
+    "episode_count": 3
+  },
+  "store_count": 2,
+  "stores": [
+    {
+      "audit_event_count": 1,
+      "episode_count": 1,
+      "store_kind": "local_graph"
+    },
+    {
+      "audit_event_count": 0,
+      "episode_count": 2,
+      "store_kind": "ops_warden_coordination"
+    }
+  ]
+}