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>

CHANGELOG.md

@@ -7,19 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-## [0.4.0] - 2026-01-17
-
 ### Fixed
 
 - **Orphan cleanup skips valid tmux sessions** - `gt orphans kill` and automatic orphan cleanup now check for Claude processes belonging to valid Gas Town tmux sessions (gt-*/hq-*) before killing. This prevents false kills of witnesses, refineries, and deacon during startup when they may temporarily show TTY "?"
 
-## [0.3.1] - 2026-01-17
-
-### Fixed
-
-- **Orphan cleanup on macOS** - Fixed TTY comparison (`??` vs `?`) so orphan detection works on macOS
-- **Session kill leaves orphans** - `gt done` and `gt crew stop` now use `KillSessionWithProcesses` to properly terminate all child processes before killing the tmux session
-
 ## [0.3.0] - 2026-01-17
 
 ### Added