feat(done): Add conflict resolution tracking fields to MR beads (gt-si8rq.7)

Add retry_count, last_conflict_sha, and conflict_task_id fields to MR bead
descriptions when created via `gt done`. These are initialized at creation
time and will be updated by the Refinery when handling merge conflicts.

- retry_count: 0 (number of conflict-resolution cycles)
- last_conflict_sha: null (SHA of main when conflict occurred)
- conflict_task_id: null (link to conflict-resolution task if any)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/cmd/done.go

@@ -225,6 +225,11 @@ func runDone(cmd *cobra.Command, args []string) error {
 				description += fmt.Sprintf("\nagent_bead: %s", agentBeadID)
 			}
 
+			// Add conflict resolution tracking fields (initialized, updated by Refinery)
+			description += "\nretry_count: 0"
+			description += "\nlast_conflict_sha: null"
+			description += "\nconflict_task_id: null"
+
 			// Create MR bead (ephemeral wisp - will be cleaned up after merge)
 			mrIssue, err := bd.Create(beads.CreateOptions{
 				Title:       title,