Silent yield failures

### What happened?

[ACTION REQUIRED] 📎 PLEASE ATTACH THE EXPORTED CHAT HISTORY JSON FILE TO THIS ISSUE IF YOU FEEL COMFORTABLE SHARING IT.

### What did you expect to happen?

I expected the tool to have a consistent back and forth with me and once a plan was approved that it would be executed. If the plan was unable to be executed I expected the tool to output some kind of error text or a message stating why actions were not completed and what information was needed from me.

### Client information

* **CLI Version:** 0.51.0
* **Git Commit:** 8d951de38
* **Session ID:** fb4f4143-388b-400a-98e2-8d78b43557d8
* **Operating System:** linux v26.0.0
* **Sandbox Environment:** no sandbox
* **Model Version:** auto
* **Auth Type:** vertex-ai
* **Memory Usage:** 555.5 MB
* **Terminal Name:** xterm.js(6.1.0-beta.213)
* **Terminal Background:** #191a1b
* **Kitty Keyboard Protocol:** Supported
* **IDE Client:** VS Code

### Login information

Vertex AI

### Anything else we need to know?

_No response_

No source file, test, or entry point is identified. Start by reproducing the silent failure with CLI version 0.51.0 using the exported chat history JSON if available, then trace why an approved plan produces no result or error. Done means identifying the failure condition and reporting a clear error or explanation when actions are not completed.

Written by the indexing model from the issue text.