feat: add PowerShell support for Windows

[knoff]

• Created scripts/convert.ps1, scripts/install.ps1, and scripts/lint-agents.ps1 for Windows environments.
• Updated README.md with clear, separated instructions for Linux/macOS (Bash) and Windows (PowerShell).

What does this PR do?

feat: Windows support via PowerShell scripts

Summary
Resolves #153.
This PR adds native support for Windows environments by providing PowerShell script alternatives to the original Bash scripts. It also refactors the documentation to clearly distinguish between Linux/macOS and Windows instructions.

Changes

New PowerShell Scripts
scripts/convert.ps1: Converted logic from convert.sh to handle agent transformations for various tools.
scripts/install.ps1: Interactive installer for Windows that auto-detects tools like Claude Code, Cursor, Aider, etc.
scripts/lint-agents.ps1: Ported linting logic to validate agent markdown files.

Documentation Refactoring
README.md now uses explicit platform-specific sections (#### Linux / macOS (Bash) and #### Windows (PowerShell)) to prevent confusion and provide clear, actionable commands for both environments.

Agent Information (if adding/modifying an agent)

No agents added or modified

Checklist

• [] Follows the agent template structure from CONTRIBUTING.md
• [] Includes YAML frontmatter with name, description, color
• [] Has concrete code/template examples (for new agents)
• Tested in real scenarios
• Proofread and formatted correctly

🗺️ Future Roadmap (Post-Merge Enhancements)

To keep this PR minimalist and easy to review, I've focused strictly on core parity and UTF-8 stability. However, I have several follow-up enhancements already developed and tested, which I plan to submit after this base support is merged:

1. Selective Agent Installation: A configuration-driven approach allowing users to choose exactly which agents to install via agents.txt.
2. Native Uninstaller: A scripts/uninstall.ps1 script for clean and safe removal of agents from all supported tools.
3. Enhanced Orchestrator: Windows-optimized tuning for the Agency Orchestrator, including dynamic roster management.
4. Improved DX: Additional linting and maintenance tools specifically for the PowerShell environment.

These features are built on top of this PR's architecture and are ready to be proposed as logical next steps.

[msitarzewski]

Hey @knoff — thanks for this. Solid work replicating the bash behavior.

Heads up: we now have four PRs for Windows support (#171, #172, #190, #191) across two approaches (PowerShell vs Python). I've left a comment on #153 asking all four contributors to converge on a single PR. Would appreciate your input there!