feat: add cron tool integration with agent

- Add adhocore/gronx dependency for cron expression parsing
- Fix CronService race conditions and add cron expression support
- Add CronTool with add/list/remove/enable/disable actions
- Add ContextualTool interface for tools needing channel/chatID context
- Add ProcessDirectWithChannel to AgentLoop for cron job execution
- Register CronTool in gateway and wire up onJob handler
- Fix slice bounds panic in addJob for short messages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/tools/registry.go

@@ -34,6 +34,10 @@ func (r *ToolRegistry) Get(name string) (Tool, bool) {
 }
 
 func (r *ToolRegistry) Execute(ctx context.Context, name string, args map[string]interface{}) (string, error) {
+	return r.ExecuteWithContext(ctx, name, args, "", "")
+}
+
+func (r *ToolRegistry) ExecuteWithContext(ctx context.Context, name string, args map[string]interface{}, channel, chatID string) (string, error) {
 	logger.InfoCF("tool", "Tool execution started",
 		map[string]interface{}{
 			"tool": name,
@@ -49,6 +53,11 @@ func (r *ToolRegistry) Execute(ctx context.Context, name string, args map[string
 		return "", fmt.Errorf("tool '%s' not found", name)
 	}
 
+	// If tool implements ContextualTool, set context
+	if contextualTool, ok := tool.(ContextualTool); ok && channel != "" && chatID != "" {
+		contextualTool.SetContext(channel, chatID)
+	}
+
 	start := time.Now()
 	result, err := tool.Execute(ctx, args)
 	duration := time.Since(start)