feat(1001): recover_half_written_items MCP tool

Adds db::recover, a discovery + recovery layer for pipeline items that
got half-written before the Stage 1 fix landed (content in content
store + SQLite shadow, no live CRDT entry). For each orphan, the
content body is re-anchored to a fresh non-tombstoned id and the old
id's content row is cleared.

Exposed as the recover_half_written_items MCP tool. dry_run defaults
to true so the caller can review what would change before mutating.

YAML front-matter parsing is hand-rolled and scoped to the three
fields the create_*_file path emits (name, type, depends_on). It
tolerates missing or malformed lines by falling back to safe
defaults; the orphan is recovered with the best metadata we can pull
from the body and the rest is left to the operator to fix up.

The discovery step is read-only and idempotent. Recovery is also
idempotent in the sense that once an orphan is lifted, the next
discovery pass won't see it.

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

server/src/http/mcp/tools_list/mod.rs

@@ -96,6 +96,7 @@ mod tests {
         assert!(names.contains(&"status"));
         assert!(names.contains(&"loc_file"));
         assert!(names.contains(&"dump_crdt"));
+        assert!(names.contains(&"recover_half_written_items"));
         assert!(names.contains(&"get_version"));
         assert!(names.contains(&"remove_criterion"));
         assert!(names.contains(&"mesh_status"));
@@ -106,7 +107,7 @@ mod tests {
         assert!(names.contains(&"show_epic"));
         assert!(names.contains(&"freeze_story"));
         assert!(names.contains(&"unfreeze_story"));
-        assert_eq!(tools.len(), 74);
+        assert_eq!(tools.len(), 75);
     }
 
     #[test]