feat: Add free-tier IDE support (Antigravity/Gemini) with model switching

[getsal]

Motivation

The original framework requires Claude Code (paid subscription), which creates a barrier to entry for developers who want to explore the framework before committing financially.

This PR adds support for free-tier alternatives while preserving Claude Code compatibility.

What's New

• ✅ Antigravity + Gemini support (tested and working)
• ✅ Model switching utility (./scripts/update-models.sh)
• ✅ Cursor IDE integration (.cursorrules)
• ✅ Claude Code compatibility preserved (untested - community verification needed)

Changes

1. Unified Agent Configuration

• Created .agents/ as single source of truth
• IDE-specific symlinks: .claude/ → .agents/, .gemini/ → .agents/
• Enables code reuse across multiple IDEs

2. Model Switching Script

bash
# Switch to Gemini
./scripts/update-models.sh gemini
# Switch to Claude
./scripts/update-models.sh claude

Updates all 8 agent definitions automatically.

3. Cursor Integration

• Added
  .cursorrules
  for Cursor AI guidance
• Works with the existing agent framework

4. Documentation Updates

• Multi-IDE setup instructions
• Clear prerequisites for each option
• Model-agnostic language

Testing Status

• ✅ Antigravity + Gemini 1.5 Pro: Fully tested and working
• ⏳ Claude Code: Untested (requires paid subscription)
  • Symlink approach should work in theory
  • Community help wanted! If you have Claude Code access, please test and report back

Backward Compatibility

• ✅ .claude/ directory preserved (via symlink)
• ✅ All agent prompts unchanged
• ✅ Workflow remains identical
• ✅ No breaking changes

Value Proposition

This PR lowers the barrier to entry by enabling developers to:

1. Try the framework for free with Gemini
2. Switch models easily as needs change
3. Upgrade to Claude when ready (no migration needed)

Notes

• Renamed
  CLAUDE.md
  →
  AGENTS.md
  to reflect model independence
• CLAUDE.md
  now symlinks to AGENTS.md for backward compatibility