Add deep links for skills and Automations

### Feature summary
Add reviewed deep-link flows for skills and Automations.

### What problem are you trying to solve?
Other apps and websites cannot open GitHub Copilot with a skill ready to add or a prefilled Automation ready to configure.

### Proposed solution
Support deep links that open GitHub Copilot with:

1. A skill ready to add from a supported source.
2. A prefilled Automation containing its name, prompt, schedule, and project.

Both flows must require user review and confirmation before making changes, consistent with existing prompt and plugin deep links.

### Workflow impact
This lets external apps and websites hand off skill installation and Automation setup without bypassing user control.

### Installation context
N/A

### Additional context
Follow the review-and-confirm interaction used by existing prompt and plugin deep links.

Inizia tracciando i flussi esistenti di deep link di prompt e plugin a cui fa riferimento l’issue. Definisci gli input dei link skill e Automation, quindi verifica che entrambi aprano un flusso verificato e precompilato e richiedano una conferma prima che vengano apportate modifiche.

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