feat(roles): switch daemon to config-based roles, remove role beads (Phase 2+3)

Phase 2: Daemon now uses config.LoadRoleDefinition() instead of role beads
- lifecycle.go: getRoleConfigForIdentity() reads from TOML configs
- Layered override resolution: builtin → town → rig

Phase 3: Remove role bead creation and references
- Remove RoleBead field from AgentFields struct
- gt install no longer creates role beads
- Remove 'role' from custom types list
- Delete migrate_agents.go (no longer needed)
- Deprecate beads_role.go (kept for reading existing beads)
- Rewrite role_beads_check.go to validate TOML configs

Existing role beads are orphaned but harmless.

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

internal/polecat/manager.go

@@ -353,7 +353,6 @@ func (m *Manager) AddWithOptions(name string, opts AddOptions) (*Polecat, error)
 		RoleType:   "polecat",
 		Rig:        m.rig.Name,
 		AgentState: "spawning",
-		RoleBead:   beads.RoleBeadIDTown("polecat"),
 		HookBead:   opts.HookBead, // Set atomically at spawn time
 	})
 	if err != nil {
@@ -648,7 +647,6 @@ func (m *Manager) RepairWorktreeWithOptions(name string, force bool, opts AddOpt
 		RoleType:   "polecat",
 		Rig:        m.rig.Name,
 		AgentState: "spawning",
-		RoleBead:   beads.RoleBeadIDTown("polecat"),
 		HookBead:   opts.HookBead, // Set atomically at spawn time
 	})
 	if err != nil {