Unable to rename branch in plan mode

### Short summary

Plan mode fails to rename the worktree branch and this blocks plan.md from being created

### Affected version or release

v1.1.14

### Installation context

Windows

### What happened?

In plan mode, the session fails to rename the branch name as it reports the branch name tool is unavailable. This leads to the plan not being created until forced to by yet another prompt.

### Steps to reproduce

1. Start session in repo worktree in plan mode
2. Prompt for a task (I used GPT-5.6 Sol Medium reasoning 400k)
3. Notice how it fails to rename branch and therefore won't make changes in the repo workspace
4. Ask it to create the plan anyway
5. Plan created

### Expected behavior

_No response_

### Additional context

Comienza reproduciendo el fallo en Windows v1.1.14, en un worktree de un repositorio y usando el modo de planificación. Sigue el flujo del cambio de nombre de la rama en el modo de planificación y de la disponibilidad de la herramienta branch-name; después, verifica que la rama cambie de nombre y que plan.md se cree sin un prompt adicional.

Escrito por el modelo de indexación a partir del texto del issue.