Previously, clicking the trash icon on the Skills settings page
immediately moved the skill's directory to the trash.

This PR now shows a confirmation prompt explains what will be deleted
and where it's shared before anything is moved to the trash. This is
because that directory is shared with other agent tools
(`~/.agents/skills` or `{project}/.agents/skills`), deleting it silently
affects more than just Zed, I think it's better to explain that.

<img height="250" alt="global-skill-delete"
src="https://github.com/user-attachments/assets/d49ecc92-c195-42d2-924e-6fb9d024d2ec"
/>
<img height="250" alt="project-skill-delete"
src="https://github.com/user-attachments/assets/4b84af28-b8fd-4635-afe5-c1cd73d09e1a"
/>

Release Notes:

- Added a confirmation prompt when deleting skills from the settings
window.