feat (auth): CLI OAuth supports pasting callback URLs to complete login

- Added callback URL resolution and terminal prompt logic
  - Codex/Claude/iFlow/Antigravity/Gemini login supports callback URL or local callback completion
  - Update Gemini login option signature and manager call
  - CLI default prompt function is compatible with null input to continue waiting

internal/cmd/openai_login.go

@@ -35,12 +35,17 @@ func DoCodexLogin(cfg *config.Config, options *LoginOptions) {
 		options = &LoginOptions{}
 	}
 
+	promptFn := options.Prompt
+	if promptFn == nil {
+		promptFn = defaultProjectPrompt()
+	}
+
 	manager := newAuthManager()
 
 	authOpts := &sdkAuth.LoginOptions{
 		NoBrowser: options.NoBrowser,
 		Metadata:  map[string]string{},
-		Prompt:    options.Prompt,
+		Prompt:    promptFn,
 	}
 
 	_, savedPath, err := manager.Login(context.Background(), "codex", cfg, authOpts)