feat(governance): trace km stale ratio rechecks

apps/api/src/models/governance.py

@@ -154,6 +154,14 @@ class KnowledgeReviewDraftArchiveRequest(BaseModel):
     dry_run: bool = False
 
 
+class KnowledgeReviewDraftStaleRatioSnapshot(BaseModel):
+    stale_count: int
+    total_count: int
+    stale_ratio: float
+    threshold: float
+    stale_days: int
+
+
 class KnowledgeReviewDraftArchiveResponse(BaseModel):
     schema_version: str = "km_review_draft_archive_v1"
     governance_event_id: str
@@ -169,6 +177,14 @@ class KnowledgeReviewDraftArchiveResponse(BaseModel):
     writes_km: bool
     writes_governance_audit: bool
     audit_dispatch_id: str | None = None
+    stale_ratio_snapshot: KnowledgeReviewDraftStaleRatioSnapshot | None = None
+    stale_ratio_recheck_status: Literal[
+        "dry_run",
+        "completed",
+        "already_active",
+        "not_requested",
+    ] = "not_requested"
+    stale_ratio_recheck_dispatch_id: str | None = None
     next_action: str = "stale_ratio_recheck"
     generated_at: datetime