fix: use rig prefixes for agent bead IDs

Align rig-scoped agent beads with route prefixes so crew add/prime/status resolve the same IDs across rigs. Add tests that assert rig-prefixed agent IDs in prime and status.

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

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

internal/cmd/crew_add.go

@@ -100,7 +100,8 @@ func runCrewAdd(cmd *cobra.Command, args []string) error {
 		fmt.Printf("  Branch: %s\n", worker.Branch)
 
 		// Create agent bead for the crew worker
-		crewID := beads.CrewBeadID(rigName, name)
+		prefix := beads.GetPrefixForRig(townRoot, rigName)
+		crewID := beads.CrewBeadIDWithPrefix(prefix, rigName, name)
 		if _, err := bd.Show(crewID); err != nil {
 			// Agent bead doesn't exist, create it
 			fields := &beads.AgentFields{