Add Zed and Antigravity editor support

[bcotrim]

Related issues

• Supersedes Added Google Antigravity and fix the grammars #2111

Proposed Changes

• Add Zed editor support (fast, Rust-based editor now available on all platforms)
• Add Google Antigravity editor support (Google's AI-powered IDE)

Testing Instructions

• Install Zed and/or Antigravity on your machine
• Open Studio settings and change preferred editor to Zed/Antigravity and save
• Navigate to a site Overview tab and confirm the option to open in your selected editor appears
• Clicking the button works as expected and opens the editor on the site root

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing bc50495 vs trunk

site-editor

Metric	trunk	bc50495	Diff	Change
load	2882.00 ms	2860.00 ms	-22.00 ms	🟢 -0.8%

site-startup

Metric	trunk	bc50495	Diff	Change
siteCreation	7120.00 ms	7084.00 ms	-36.00 ms	🟢 -0.5%
siteStartup	3922.00 ms	3932.00 ms	+10.00 ms	🔴 0.3%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change