fs: refactor agent ctl to map-based dispatch

Replace switch statement with rdwrHandler map. Each command is a
function value in agentCtlHandlers — easy to extend, test individually,
and introspect.

fs/handlers.go

@@ -664,34 +664,49 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 	cmd := parts[0]
 	args := parts[1:]
 
-	switch cmd {
-	case "kill":
+	h, ok := agentCtlHandlers[cmd]
+	if !ok {
+		return nil, fmt.Errorf("unknown ctl command: %s", cmd)
+	}
+	return h(ctx, args)
+}
+
+// rdwrHandler is a request-response ctl command handler.
+type rdwrHandler func(ctx HandlerCtx, args []string) ([]byte, error)
+
+var agentCtlHandlers = map[string]rdwrHandler{
+	"kill": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		if ctx.Session.Core != nil {
 			ctx.Session.Core.RemoveAgent(ctx.Agent.ID())
 			session.PublishEvent("session."+ctx.Session.ID()+".agent."+ctx.Agent.ID()+".kill", "")
 		}
 		return []byte("ok\n"), nil
-	case "stop":
+	},
+	"stop": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		ctx.Agent.Interrupt(agent.ErrInterrupted)
 		return []byte("ok\n"), nil
-	case "compact":
+	},
+	"compact": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		if err := ctx.Agent.Compact(ctx.Session.Ctx()); err != nil {
 			return nil, err
 		}
 		return []byte("ok\n"), nil
-	case "clear":
+	},
+	"clear": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		if err := ctx.Agent.Clear(); err != nil {
 			return nil, err
 		}
 		return []byte("ok\n"), nil
-	case "inject":
+	},
+	"inject": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		text := strings.Join(args, " ")
 		if text == "" {
 			return nil, fmt.Errorf("inject requires text")
 		}
 		ctx.Agent.InjectRewrite(text)
 		return []byte("ok\n"), nil
-	case "agent":
+	},
+	"agent": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			return []byte(ctx.Agent.Profile() + "\n"), nil
 		}
@@ -699,7 +714,8 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 			return nil, err
 		}
 		return []byte(args[0] + "\n"), nil
-	case "model":
+	},
+	"model": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			if be := ctx.Agent.Backend(); be != nil {
 				return []byte(be.Model() + "\n"), nil
@@ -710,9 +726,11 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 			be.SetModel(strings.Join(args, " "))
 		}
 		return []byte(strings.Join(args, " ") + "\n"), nil
-	case "models":
+	},
+	"models": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		return []byte(ctx.Session.CachedListModels() + "\n"), nil
-	case "tools":
+	},
+	"tools": func(ctx HandlerCtx, _ []string) ([]byte, error) {
 		if ctx.Session.ToolsConn() == nil {
 			return []byte("(no tool server)\n"), nil
 		}
@@ -729,7 +747,8 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 			}
 		}
 		return []byte(sb.String()), nil
-	case "tool_load":
+	},
+	"tool_load": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			return nil, fmt.Errorf("tool_load requires a tool name")
 		}
@@ -737,22 +756,24 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 			return nil, err
 		}
 		return []byte(args[0] + "\n"), nil
-	case "backend":
+	},
+	"backend": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			if be := ctx.Agent.Backend(); be != nil {
 				return []byte(be.Name() + "\n"), nil
 			}
 			return nil, nil
 		}
-		// backend switching not supported via ctl (requires session-level setup)
 		return nil, fmt.Errorf("backend switching not supported via ctl; use cfg")
-	case "name":
+	},
+	"name": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			return []byte(ctx.Agent.Name() + "\n"), nil
 		}
 		ctx.Agent.SetName(strings.Join(args, " "))
 		return []byte(strings.Join(args, " ") + "\n"), nil
-	case "cwd":
+	},
+	"cwd": func(ctx HandlerCtx, args []string) ([]byte, error) {
 		if len(args) == 0 {
 			return []byte(ctx.Agent.Cwd() + "\n"), nil
 		}
@@ -762,9 +783,7 @@ func requestAgentCtl(ctx HandlerCtx, data []byte) ([]byte, error) {
 		}
 		ctx.Agent.SetCWD(dir)
 		return []byte(dir + "\n"), nil
-	default:
-		return nil, fmt.Errorf("unknown ctl command: %s", cmd)
-	}
+	},
 }
 
 func readAgentStats(ctx HandlerCtx) ([]byte, error) {