fix(agent): tie MCP connections to agent lifecycle context

- Defer MCP server initialization to Run() using agent's context
- Add mcpConfig and mcpInitOnce fields to AgentLoop
- Use sync.Once to ensure MCP loads exactly once with proper context
- Prevents orphaned subprocesses and resource leaks on cancellation

This fixes GitHub Copilot feedback that MCP connections with
context.Background() won't terminate when the agent stops, causing
potential resource leaks and orphaned stdio/SSE connections.

pkg/agent/loop.go

@@ -42,7 +42,9 @@ type AgentLoop struct {
 	state          *state.Manager
 	contextBuilder *ContextBuilder
 	tools          *tools.ToolRegistry
-	mcpManager     *mcp.Manager // MCP server manager for resource cleanup
+	mcpManager     *mcp.Manager     // MCP server manager for resource cleanup
+	mcpConfig      *config.Config   // Config for lazy MCP initialization
+	mcpInitOnce    sync.Once        // Ensures MCP is initialized only once
 	running        atomic.Bool
 	summarizing    sync.Map // Tracks which sessions are currently being summarized
 	channelManager *channels.Manager
@@ -129,15 +131,9 @@ func NewAgentLoop(cfg *config.Config, msgBus *bus.MessageBus, provider providers
 
 	restrict := cfg.Agents.Defaults.RestrictToWorkspace
 
-	// Initialize MCP Manager and load servers
+	// Create MCP Manager (actual server loading deferred to Run())
+	// This ensures MCP connections use the agent's lifecycle context
 	mcpManager := mcp.NewManager()
-	ctx := context.Background()
-	if err := mcpManager.LoadFromConfig(ctx, cfg); err != nil {
-		logger.WarnCF("agent", "Failed to load MCP servers, MCP tools will not be available",
-			map[string]interface{}{
-				"error": err.Error(),
-			})
-	}
 
 	// Create tool registry for main agent
 	toolsRegistry := createToolRegistry(workspace, restrict, cfg, msgBus, mcpManager)
@@ -177,6 +173,7 @@ func NewAgentLoop(cfg *config.Config, msgBus *bus.MessageBus, provider providers
 		contextBuilder: contextBuilder,
 		tools:          toolsRegistry,
 		mcpManager:     mcpManager,
+		mcpConfig:      cfg, // Store config for lazy initialization in Run()
 		summarizing:    sync.Map{},
 	}
 }
@@ -184,6 +181,17 @@ func NewAgentLoop(cfg *config.Config, msgBus *bus.MessageBus, provider providers
 func (al *AgentLoop) Run(ctx context.Context) error {
 	al.running.Store(true)
 
+	// Initialize MCP servers using the agent's lifecycle context
+	// This ensures MCP connections are cancelled when the agent stops
+	al.mcpInitOnce.Do(func() {
+		if err := al.mcpManager.LoadFromConfig(ctx, al.mcpConfig); err != nil {
+			logger.WarnCF("agent", "Failed to load MCP servers, MCP tools will not be available",
+				map[string]interface{}{
+					"error": err.Error(),
+				})
+		}
+	})
+
 	for al.running.Load() {
 		select {
 		case <-ctx.Done():