fix(precedents): auto-clear *_requested_at on terminal status

set_case_law_extraction_status and set_case_law_halacha_status now NULL
the corresponding *_requested_at timestamp when status transitions to
"completed" or "failed". Without this, completed rows kept lingering in
the local-MCP work queue (which scans by `WHERE *_requested_at IS NOT NULL`)
and the UI's isPrecedentActive check, leaving them undeletable until a
manual SQL cleanup.

The pre-existing process_pending_extractions path already called
clear_extraction_request, but other paths (re-extraction, status set
during upload) didn't — so the cleanup belongs at the status setter.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/db.py

@@ -1774,7 +1774,19 @@ async def update_case_law(case_law_id: UUID, **fields) -> dict | None:
 
 
 async def set_case_law_extraction_status(case_law_id: UUID, status: str) -> None:
+    """Set text-extraction status. When transitioning to a terminal state
+    ('completed'/'failed') we also NULL ``metadata_extraction_requested_at``
+    so the local-MCP queue (`process_pending_extractions`, which scans by
+    ``WHERE *_requested_at IS NOT NULL``) doesn't re-pick the row forever
+    and leave the row blocked in the UI's `isPrecedentActive` check."""
     pool = await get_pool()
+    if status in ("completed", "failed"):
+        await pool.execute(
+            "UPDATE case_law SET extraction_status = $2, "
+            "metadata_extraction_requested_at = NULL WHERE id = $1",
+            case_law_id, status,
+        )
+    else:
         await pool.execute(
             "UPDATE case_law SET extraction_status = $2 WHERE id = $1",
             case_law_id, status,
@@ -1782,7 +1794,17 @@ async def set_case_law_extraction_status(case_law_id: UUID, status: str) -> None
 
 
 async def set_case_law_halacha_status(case_law_id: UUID, status: str) -> None:
+    """Set halacha-extraction status. Mirrors ``set_case_law_extraction_status``:
+    on terminal states we also clear ``halacha_extraction_requested_at`` so the
+    queue and UI don't see a stale request flag."""
     pool = await get_pool()
+    if status in ("completed", "failed"):
+        await pool.execute(
+            "UPDATE case_law SET halacha_extraction_status = $2, "
+            "halacha_extraction_requested_at = NULL WHERE id = $1",
+            case_law_id, status,
+        )
+    else:
         await pool.execute(
             "UPDATE case_law SET halacha_extraction_status = $2 WHERE id = $1",
             case_law_id, status,