Add Antigravity CLI skills, hooks, and icon

[uvayankee]

What problem does this solve?

Antigravity CLI does not have tailored hooks to move worktrees to an 'active' state inside of supacode, or skills to control the supacode cli.

Proposed solution

Add antigravity to the Agent Integration switcher, and develop an installation component that parallels the other available CLIs. The Antigravity CLI has documented PreInvocation and PostInvocation hooks, as well as PreToolUse and PostToolUse. I have tested that supacode and antigravity will work together using the hook and skill pattern developed in this repo for other cli agents.

Alternatives considered

No response

Supacode version

No response

Are you planning to build this yourself?

• I intend to open a pull request once this is approved and marked ready.

Before submitting

• I searched existing issues and this is not a duplicate.
• I understand feature pull requests are closed until the issue is marked ready.
• I agree to follow this project's Code of Conduct.

[github-actions]

Thank you for filing this. A maintainer will review it and follow up here.

Please do not start any work or open a pull request until this issue is labeled ready. That label is a maintainer's go-ahead: a pull request opened against an issue that is not yet ready is labeled invalid until then. You will get a comment here the moment it is marked ready.

See CONTRIBUTING.md for the full flow.

[github-actions]

Thanks for your patience. This is approved and marked ready, so it is now open for a pull request. If you'd like to work on it, open a pull request and link it with Closes #711 in the description. If the issue is assigned to someone, it is reserved for them; otherwise anyone is welcome to pick it up.

See CONTRIBUTING.md for the full flow.

[rash2104]

Much needed @uvayankee are you working on this?

[uvayankee]

I have it running locally and should have a branch up soon - travelling today or it'd already be there.