refactor: extract Close fork cleanup to closeExt in loop_ext.go

Move done channel close, stats flush, and sessions close into
closeExt(). Close() now calls closeExt() + MCP/registry close.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/agent/loop.go

@@ -520,15 +520,7 @@ func (al *AgentLoop) Stop() {
 // and dirty session data). Should be called during graceful shutdown.
 
 func (al *AgentLoop) Close() {
-	select {
-	case <-al.done:
-
-		// already closed
-
-	default:
-
-		close(al.done)
-	}
+	al.closeExt()
 
 	mcpManager := al.mcp.takeManager()
 	if mcpManager != nil {
@@ -540,18 +532,7 @@ func (al *AgentLoop) Close() {
 		}
 	}
 
-	if al.stats != nil {
-		al.stats.Close()
-	}
-
-	registry := al.GetRegistry()
-	for _, agentID := range registry.ListAgentIDs() {
-		if agent, ok := registry.GetAgent(agentID); ok {
-			agent.Sessions.Close()
-		}
-	}
-
-	registry.Close()
+	al.GetRegistry().Close()
 }
 
 func (al *AgentLoop) RegisterTool(tool tools.Tool) {

pkg/agent/loop_ext.go

@@ -75,6 +75,28 @@ func (al *AgentLoop) initLoopExt(cfg *config.Config, registry *AgentRegistry, en
 	go al.gcLoop()
 }
 
+// closeExt releases fork-specific resources: done channel, stats tracker,
+// and session stores for all agents.
+func (al *AgentLoop) closeExt() {
+	select {
+	case <-al.done:
+		// already closed
+	default:
+		close(al.done)
+	}
+
+	if al.stats != nil {
+		al.stats.Close()
+	}
+
+	registry := al.GetRegistry()
+	for _, agentID := range registry.ListAgentIDs() {
+		if agent, ok := registry.GetAgent(agentID); ok {
+			agent.Sessions.Close()
+		}
+	}
+}
+
 // SetConfigSaver registers a callback to persist config changes.
 func (al *AgentLoop) SetConfigSaver(fn func(*config.Config) error) {
 	al.saveConfig = fn