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

Inizia riproducendo il problema in Windows v1.1.14, in un worktree di un repository e usando la modalità piano. Traccia quindi il flusso di rinomina del branch nella modalità piano e della disponibilità dello strumento branch-name; verifica infine che il branch venga rinominato e che plan.md venga creato senza un prompt aggiuntivo.

Scritto dal modello di indicizzazione a partire dal testo della issue.