feat(governance): surface stale km burndown

apps/api/src/models/governance.py

@@ -376,6 +376,47 @@ class KnowledgeStaleOwnerReviewInboxResponse(BaseModel):
     generated_at: datetime
 
 
+class KnowledgeStaleOwnerReviewBurnDownItem(BaseModel):
+    completion_dispatch_id: str
+    governance_event_id: str
+    source_dispatch_id: str | None = None
+    recheck_dispatch_id: str | None = None
+    entry_id: str | None = None
+    project_id: str
+    dispatch_status: str
+    workflow_stage: str
+    review_outcome: Literal[
+        "refresh_with_evidence",
+        "archive",
+        "supersede",
+    ] | None = None
+    owner: str | None = None
+    completed_at: datetime | None = None
+    stale_ratio_snapshot: KnowledgeReviewDraftStaleRatioSnapshot | None = None
+    stale_count_delta: int | None = None
+    stale_ratio_delta: float | None = None
+    above_threshold: bool | None = None
+
+
+class KnowledgeStaleOwnerReviewBurnDownResponse(BaseModel):
+    schema_version: str = "km_stale_owner_review_burndown_v1"
+    project_id: str
+    burn_down_status: Literal["above_threshold", "at_or_below_threshold", "no_data"]
+    current_snapshot: KnowledgeReviewDraftStaleRatioSnapshot | None = None
+    entries_to_threshold: int
+    pending_owner_reviews: int
+    completed_owner_reviews: int
+    completion_audit_total: int
+    stale_ratio_recheck_total: int
+    latest_stale_count_delta: int | None = None
+    latest_stale_ratio_delta: float | None = None
+    writes_on_read: bool = False
+    manual_review_required: bool = True
+    returned: int
+    items: list[KnowledgeStaleOwnerReviewBurnDownItem] = Field(default_factory=list)
+    generated_at: datetime
+
+
 class KnowledgeStaleOwnerReviewCompleteRequest(BaseModel):
     dispatch_id: str | None = Field(
         default=None,