feat(db): Add cleanup_stale_anonymous_tasks function

Add a database function to delete anonymous tasks (tasks with contract_id = NULL)
that are in a terminal state (done, failed, merged) and older than a specified
number of days. This helps prevent accumulation of orphaned tasks that were created
for ad-hoc operations like task branching.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/makima/src/db/repository.rs b/makima/src/db/repository.rs
index 33e48a4..7387735 100644
--- a/makima/src/db/repository.rs
+++ b/makima/src/db/repository.rs
@@ -3684,3 +3684,31 @@ pub async fn get_supervisor_conversation_full(
 ) -> Result<Option<SupervisorState>, sqlx::Error> {
     get_supervisor_state(pool, contract_id).await
 }
+
+// =============================================================================
+// Anonymous Task Cleanup Functions
+// =============================================================================
+
+/// Delete stale anonymous tasks (tasks with contract_id = NULL) that:
+/// - Are in a terminal state (done, failed, merged)
+/// - Are older than the specified number of days
+///
+/// Returns the number of deleted tasks.
+pub async fn cleanup_stale_anonymous_tasks(
+    pool: &PgPool,
+    max_age_days: i32,
+) -> Result<i64, sqlx::Error> {
+    let result = sqlx::query(
+        r#"
+        DELETE FROM tasks
+        WHERE contract_id IS NULL
+          AND status IN ('done', 'failed', 'merged')
+          AND created_at < NOW() - INTERVAL '1 day' * $1
+        "#,
+    )
+    .bind(max_age_days)
+    .execute(pool)
+    .await?;
+
+    Ok(result.rows_affected() as i64)
+}