feat: add install_antigravity.ps1 for seamless agent-to-skill conversion

[nabeel-workspace]

PR Description: Add PowerShell Installer for Antigravity

What does this PR do?

This PR introduces scripts/install_antigravity.ps1, a native Windows PowerShell utility designed to help Windows users seamlessly integrate Agency Agents into the Antigravity (Gemini) environment. While previously restricted to shell-based environments, this script brings full cross-platform parity by offering:

• Native Windows Support: Specifically built for PowerShell, removing the need for WSL or Git Bash on Windows machines.
• Smart Path Resolution: Uses $PSScriptRoot and $HOME to automatically detect your plugin folder and your Antigravity skills directory without any manual configuration.
• Automated Scanning: Scans all 15 agent category folders (now including strategy) for markdown files.
• Dynamic Conversion: Automatically extracts YAML frontmatter, slugifies skill names with the agency- prefix, and injects required metadata.
• Preview Mode: Includes a -DryRun switch so users can safely test the script's logic and path resolution before any files are written.

Why this is needed?

Providing a PowerShell variant ensures that Windows developers can contribute and use these agents with zero friction, particularly for local development with Antigravity / Gemini where file paths differ significantly from Linux-based systems.

Agent Information

• Agent Name: N/A (Tooling update)
• Category: scripts / integrations
• Specialty: Windows Automation & Developer Experience (DX)

Checklist

• Follows the project's scripting conventions
• Windows Native Support (PowerShell 5.1 / 7.x)
• Dynamic path resolution for public use (no hardcoded user paths)
• Support for -DryRun operation implemented
• Proofread and formatted correctly

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How to Use (On Windows):

# Preview what would be installed
.\scripts\install_antigravity.ps1 -DryRun

# Run the project-wide conversion
.\scripts\install_antigravity.ps1

[mhc222]

Code Review

No issues found.

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Reviewed by Code Reviewer agent. Issues are only reported at confidence ≥80/100.