refactor: migrate callers from deprecated MayorBeadID/DeaconBeadID to Town variants (gt-gbw0a)

Update all callers of deprecated MayorBeadID()/DeaconBeadID() to use
MayorBeadIDTown()/DeaconBeadIDTown() which return hq- prefix IDs for
town-level beads storage.

Changes:
- internal/daemon/lifecycle.go: identityToAgentBeadID and checkStaleAgents
- internal/cmd/prime.go: getAgentBeadID
- internal/cmd/molecule_status.go: buildAgentBeadID
- internal/cmd/prime_test.go: update expected values to hq-*
- Comments updated to reflect hq- prefix for town-level agents

The deprecated functions remain for backward compatibility and are used
by the migration tool (migrate_agents.go).

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

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

internal/cmd/prime_test.go

@@ -36,7 +36,7 @@ func TestGetAgentBeadID_UsesRigPrefix(t *testing.T) {
 				Role:     RoleMayor,
 				TownRoot: townRoot,
 			},
-			want: "gt-mayor",
+			want: "hq-mayor",
 		},
 		{
 			name: "deacon",
@@ -44,7 +44,7 @@ func TestGetAgentBeadID_UsesRigPrefix(t *testing.T) {
 				Role:     RoleDeacon,
 				TownRoot: townRoot,
 			},
-			want: "gt-deacon",
+			want: "hq-deacon",
 		},
 		{
 			name: "witness",