Feature Request: Add /cd command to change working directory

I'd like to suggest adding a `/cd` command to the Q CLI that allows users to change the current working directory during an active chat session.

**Current Pain Point:**
When working with Amazon Q CLI, switching between directories requires:
1. Closing the current Q session
2. Navigating to the new directory in the terminal
3. Starting a new Q session from that directory

This workflow is disruptive and breaks the conversation flow, especially when working across multiple repositories or project directories.

**Proposed Solution:**
Add a `/cd ` command (similar to existing commands like `/quit`, `/save`, etc.) that:
- Changes the working directory for all subsequent queries in the current session
- Updates the system context to reflect the new directory
- Automatically loads contextual information from the new directory (README files, project structure, etc.)

**Benefits:**
1. **Seamless workflow**: Stay in the same conversation while switching between directories
2. **Context preservation**: Maintain chat history and context while working across multiple repos
3. **Better UX**: Eliminates the need to restart sessions just to change dir

**Example Usage:**
User: /cd /path/to/another-repo
Q: Working directory changed to /path/to/another-repo
User: [continues working in the new directory context]

This would significantly improve productivity when working on multi-repository projects or when needing to reference code across different directories during a single
conversation.

Inizia individuando gli handler di Q CLI per i comandi esistenti /quit e /save, quindi segui il modo in cui la sessione attiva memorizza la propria directory di lavoro e costruisce il contesto. Esegui il comando in una sessione di chat attiva con un'altra directory e verifica che le query successive utilizzino la nuova posizione mentre la cronologia della chat viene preservata.

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