fix: exclude role and rig types from bd ready (#1105)

Role and rig beads are reference metadata that should never be closed
or appear as actionable work. They are similar to agent beads which
are already excluded.

- Add 'role' and 'rig' to the issue type exclusion list in GetReadyWork
- Update comments to document the excluded types

Fixes confusion where role/rig beads appeared in bd ready output,
leading agents to try to close them as regular work items.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/sqlite/ready.go

@@ -43,7 +43,9 @@ func (s *SQLiteStorage) GetReadyWork(ctx context.Context, filter types.WorkFilte
 		// - molecule: workflow containers
 		// - message: mail/communication items
 		// - agent: identity/state tracking beads
-		whereClauses = append(whereClauses, "i.issue_type NOT IN ('merge-request', 'gate', 'molecule', 'message', 'agent')")
+		// - role: agent role definitions (reference metadata)
+		// - rig: rig identity beads (reference metadata)
+		whereClauses = append(whereClauses, "i.issue_type NOT IN ('merge-request', 'gate', 'molecule', 'message', 'agent', 'role', 'rig')")
 	}
 
 	if filter.Priority != nil {