refactor(commands): provision slash commands at town-level only (gt-7x274)

- gt install now creates ~/gt/.claude/commands/ with all commands
- Removed per-workspace provisioning from crew/polecat managers
- Updated bd doctor to check town-level instead of per-workspace
- All agents inherit via Claude directory traversal

This eliminates duplicate /handoff skills in the picker.

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

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

internal/cmd/install.go

@@ -224,6 +224,14 @@ func runInstall(cmd *cobra.Command, args []string) error {
 		}
 	}
 
+	// Provision town-level slash commands (.claude/commands/)
+	// All agents inherit these via Claude's directory traversal - no per-workspace copies needed.
+	if err := templates.ProvisionCommands(absPath); err != nil {
+		fmt.Printf("   %s Could not provision slash commands: %v\n", style.Dim.Render("⚠"), err)
+	} else {
+		fmt.Printf("   ✓ Created .claude/commands/ (slash commands for all agents)\n")
+	}
+
 	// Initialize git if requested (--git or --github implies --git)
 	if installGit || installGitHub != "" {
 		fmt.Println()