fix(ingestion): proper error propagation and transaction safety

Three hardening improvements to the ingestion orchestrator:

- Replace .unwrap_or(0) with ? on COUNT(*) queries for total_issues
  and total_mrs. These are simple aggregate queries that should never
  fail, but if they do (e.g. table missing after failed migration),
  propagating the error gives an actionable message instead of silently
  reporting 0 items.

- Wrap store_closes_issues_refs in a SAVEPOINT with proper
  ROLLBACK/RELEASE. Previously, a failure mid-loop (e.g. on the 5th of
  10 close-issue references) would leave partial refs committed. Now
  the entire batch is atomic.

- Replace silent catch-all (_ => {}) arms in enqueue_resource_events
  and update_resource_event_watermark with explicit warnings for
  unknown entity_type values. Makes debugging easier when new entity
  types are added but the match arms aren't updated.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ingestion/orchestrator.rs

@@ -131,13 +131,11 @@ pub async fn ingest_project_issues_with_progress(
 
     let issues_needing_sync = issue_result.issues_needing_discussion_sync;
 
-    let total_issues: i64 = conn
-        .query_row(
+    let total_issues: i64 = conn.query_row(
         "SELECT COUNT(*) FROM issues WHERE project_id = ?",
         [project_id],
         |row| row.get(0),
-        )
-        .unwrap_or(0);
+    )?;
     let total_issues = total_issues as usize;
     result.issues_skipped_discussion_sync = total_issues.saturating_sub(issues_needing_sync.len());
 
@@ -346,13 +344,11 @@ pub async fn ingest_project_merge_requests_with_progress(
 
     let mrs_needing_sync = get_mrs_needing_discussion_sync(conn, project_id)?;
 
-    let total_mrs: i64 = conn
-        .query_row(
+    let total_mrs: i64 = conn.query_row(
         "SELECT COUNT(*) FROM merge_requests WHERE project_id = ?",
         [project_id],
         |row| row.get(0),
-        )
-        .unwrap_or(0);
+    )?;
     let total_mrs = total_mrs as usize;
     result.mrs_skipped_discussion_sync = total_mrs.saturating_sub(mrs_needing_sync.len());
 
@@ -573,7 +569,12 @@ fn enqueue_resource_events_for_entity_type(
                 [project_id],
             )?;
         }
-        _ => {}
+        other => {
+            warn!(
+                entity_type = other,
+                "Unknown entity_type in enqueue_resource_events, skipping stale job cleanup"
+            );
+        }
     }
 
     let entities: Vec<(i64, i64)> = match entity_type {
@@ -900,7 +901,12 @@ fn update_resource_event_watermark_tx(
                 [entity_local_id],
             )?;
         }
-        _ => {}
+        other => {
+            warn!(
+                entity_type = other,
+                "Unknown entity_type in watermark update, skipping"
+            );
+        }
     }
     Ok(())
 }
@@ -1138,6 +1144,8 @@ fn store_closes_issues_refs(
     mr_local_id: i64,
     closes_issues: &[crate::gitlab::types::GitLabIssueRef],
 ) -> Result<()> {
+    conn.execute_batch("SAVEPOINT store_closes_refs")?;
+    let inner = || -> Result<()> {
         for issue_ref in closes_issues {
             let target_local_id = resolve_issue_local_id(conn, project_id, issue_ref.iid)?;
 
@@ -1164,8 +1172,18 @@ fn store_closes_issues_refs(
 
             insert_entity_reference(conn, &ref_)?;
         }
-
         Ok(())
+    };
+    match inner() {
+        Ok(()) => {
+            conn.execute_batch("RELEASE store_closes_refs")?;
+            Ok(())
+        }
+        Err(e) => {
+            let _ = conn.execute_batch("ROLLBACK TO store_closes_refs; RELEASE store_closes_refs");
+            Err(e)
+        }
+    }
 }
 
 #[cfg(test)]