refactor: consolidate agent env vars into config.AgentEnv

Create centralized AgentEnv function as single source of truth for all
agent environment variables. All agents now consistently receive:
- GT_ROLE, BD_ACTOR, GIT_AUTHOR_NAME (role identity)
- GT_ROOT, BEADS_DIR (workspace paths)
- GT_RIG, GT_POLECAT/GT_CREW (rig-specific identity)
- BEADS_AGENT_NAME, BEADS_NO_DAEMON (beads config)
- CLAUDE_CONFIG_DIR (optional account selection)

Remove RoleEnvVars in favor of AgentEnvSimple wrapper.
Remove IncludeBeadsEnv flag - beads env vars always included.
Update all manager and cmd call sites to use AgentEnv.

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

internal/daemon/daemon.go

@@ -847,8 +847,8 @@ func (d *Daemon) restartPolecatSession(rigName, polecatName, sessionName string)
 	}
 
 	// Set environment variables
-	// Use shared RoleEnvVars for consistency across all role startup paths
-	envVars := config.RoleEnvVars("polecat", rigName, polecatName)
+	// Use centralized AgentEnvSimple for consistency across all role startup paths
+	envVars := config.AgentEnvSimple("polecat", rigName, polecatName)
 
 	// Add polecat-specific beads configuration
 	// Use ResolveBeadsDir to follow redirects for repos with tracked beads