wip(929): stage 8 — wrap reconcile review_hold FS writes in yaml_residue

The startup reconciler still pokes review_hold into the on-disk story file
when promoting human-QA items, because no CRDT register exists yet for
review_hold (filed as sub-story 932). The two write-side callsites in
reconcile.rs were the last bare yaml_legacy:: calls in production write
paths; wrap them in yaml_residue so the gap shows up in
`grep -rn yaml_residue` like the other 932/933 markers.

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

server/src/agents/pool/auto_assign/reconcile.rs

@@ -215,10 +215,15 @@ impl AgentPool {
                                 message: format!("Failed to advance to QA: {e}"),
                             });
                         } else {
+                            // Story 929 / sub-story 932: the review_hold signal still
+                            // lives in YAML on disk because no CRDT register exists.
+                            // Wrapped in `yaml_residue` so the gap is grep-findable.
                             let story_path = project_root
                                 .join(".huskies/work/3_qa")
                                 .join(format!("{story_id}.md"));
-                            if let Err(e) = crate::db::yaml_legacy::write_review_hold(&story_path) {
+                            if let Err(e) = crate::db::yaml_legacy::yaml_residue(
+                                crate::db::yaml_legacy::write_review_hold(&story_path),
+                            ) {
                                 eprintln!(
                                     "[startup:reconcile] Failed to set review_hold on '{story_id}': {e}"
                                 );
@@ -284,10 +289,14 @@ impl AgentPool {
                     };
 
                     if needs_human_review {
+                        // Story 929 / sub-story 932: see note above; review_hold
+                        // is YAML-only until the CRDT register exists.
                         let story_path = project_root
                             .join(".huskies/work/3_qa")
                             .join(format!("{story_id}.md"));
-                        if let Err(e) = crate::db::yaml_legacy::write_review_hold(&story_path) {
+                        if let Err(e) = crate::db::yaml_legacy::yaml_residue(
+                            crate::db::yaml_legacy::write_review_hold(&story_path),
+                        ) {
                             eprintln!(
                                 "[startup:reconcile] Failed to set review_hold on '{story_id}': {e}"
                             );