wip(929): stage 1 — migrate chat/commands/* off yaml_legacy

Each chat command that previously read parse_front_matter for story
metadata (name, agent, depends_on, blocked, retry_count, merge_failure,
qa_mode) now reads from the typed CRDT API:

- WorkItem (via crdt_state::read_item) for pipeline-item registers.
- MergeJobView (via crdt_state::read_merge_job) for the merge failure
  detail text, which has its own LWW-map CRDT entry.

Files migrated: depends.rs, freeze.rs, move_story.rs, overview.rs,
status/render.rs, triage.rs, unblock.rs, unreleased.rs.

unblock.rs: also removes the legacy front-matter cleanup branch that
fired when the typed Blocked→Coding transition failed. Post-929 there
is no YAML on disk to clean; the fallback now just resets retry_count
in the CRDT.

triage.rs: drops the YAML-only `review_hold` and `coverage_baseline`
fields from the dump. These have no CRDT register and were never
load-bearing on the triage output; if needed later, add a CRDT register
and surface it back.

Tests:
- The three status/render merge-failure rendering tests now seed a
  MergeJob CRDT entry via write_merge_job instead of writing YAML.
- The unblock test that asserted YAML cleanup on disk is now an assertion
  on the CRDT registers (blocked=false, retry_count=0). Also re-seeded
  in `2_blocked` stage so the typed Blocked → Coding transition actually
  fires (not the fallback path).

All 2855 tests pass; fmt clean; clippy clean.

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

server/src/chat/commands/unblock.rs

@@ -5,7 +5,6 @@
 //! and returns a confirmation.
 
 use super::CommandContext;
-use crate::db::yaml_legacy::clear_front_matter_field_in_content;
 use std::path::Path;
 
 /// Handle the `unblock` command.
@@ -80,37 +79,14 @@ fn unblock_by_story_id(story_id: &str) -> String {
     // the CRDT.
     if let Err(e) = crate::agents::lifecycle::transition_to_unblocked(story_id) {
         // If the typed transition fails (e.g. a legacy Archived item with no
-        // valid `Unblock` transition out of its current stage), fall back to
-        // a direct CRDT/content cleanup. The legacy front-matter cleanup is
-        // gated on content actually still containing YAML, so post-865
-        // CRDT-only stories don't hit a parse error.
+        // valid `Unblock` transition out of its current stage), at least
+        // reset retry_count directly in the CRDT so the agent doesn't stay
+        // tagged with a stale fail counter. Post-929 there's no FS shadow
+        // to clean up alongside.
         crate::slog_warn!(
             "[unblock] State-machine transition failed for '{story_id}': {e}. \
-             Falling back to direct CRDT cleanup."
+             Falling back to direct CRDT retry_count reset."
         );
-
-        if let Some(content) = crate::db::read_content(story_id) {
-            // Only run legacy front-matter cleanup if the stored content still
-            // begins with a `---` YAML block. Post-865 content has been
-            // stripped and would no-op here anyway.
-            if content.trim_start().starts_with("---") {
-                let mut updated = content;
-                updated = clear_front_matter_field_in_content(&updated, "blocked");
-                updated = clear_front_matter_field_in_content(&updated, "merge_failure");
-                updated = clear_front_matter_field_in_content(&updated, "retry_count");
-                crate::db::write_content(story_id, &updated);
-                let stage = typed_item
-                    .as_ref()
-                    .map(|i| i.stage.dir_name().to_string())
-                    .unwrap_or_else(|| "2_current".to_string());
-                crate::db::write_item_with_content(
-                    story_id,
-                    &stage,
-                    &updated,
-                    crate::db::ItemMeta::from_yaml(&updated),
-                );
-            }
-        }
         crate::crdt_state::set_retry_count(story_id, 0);
     }
 
@@ -221,14 +197,15 @@ mod tests {
         // global content store.
         write_story_file(
             tmp.path(),
-            "2_current",
+            "2_blocked",
             "9903_story_stuck.md",
             "---\nname: Stuck Story\nblocked: true\nretry_count: 5\n---\n# Story\n",
         );
-        // Seed the story in the CRDT with retry_count=5 so set_retry_count can reset it.
+        // Seed the story in the CRDT in 2_blocked stage so the typed
+        // Blocked → Coding transition fires and clears `blocked` properly.
         crate::crdt_state::write_item(
             "9903_story_stuck",
-            "2_current",
+            "2_blocked",
             Some("Stuck Story"),
             None,
             Some(5),
@@ -249,25 +226,9 @@ mod tests {
             "should include story_id in response: {output}"
         );
 
-        // The unblock command writes back via the content store; blocked field should be gone.
-        let contents = crate::db::read_content("9903_story_stuck")
-            .or_else(|| {
-                std::fs::read_to_string(
-                    tmp.path()
-                        .join(".huskies/work/2_current/9903_story_stuck.md"),
-                )
-                .ok()
-            })
-            .expect("story content should be readable after unblock");
-        assert!(
-            !contents.contains("blocked:"),
-            "blocked field should be removed: {contents}"
-        );
-        // retry_count is now in the CRDT, not in front-matter.
-        assert!(
-            !contents.contains("retry_count:"),
-            "retry_count should be cleared from front-matter after unblock: {contents}"
-        );
+        // Post-929: the CRDT is the sole source of truth; we no longer clean
+        // YAML front matter from on-disk content. Verify the CRDT registers
+        // were updated correctly.
         let item = crate::crdt_state::read_item("9903_story_stuck")
             .expect("story should be in CRDT after unblock");
         assert_eq!(
@@ -275,6 +236,10 @@ mod tests {
             0,
             "retry_count should be reset to 0 in CRDT after unblock"
         );
+        assert!(
+            !item.blocked(),
+            "blocked flag should be cleared in CRDT after unblock"
+        );
     }
 
     #[test]