Add native Windows support

[Teylersf]

Problem or use case

The Entire CLI currently lacks native Windows support, preventing Windows users from using the tool effectively.

Desired behavior

# Solution
Add native Windows builds with full support for Windows 10/11, all core CLI commands, Git integration, Checkpoints, Claude Code and Gemini CLI agents, and Interactive TUI.

## Technical Details
- Zero code changes required (Go's cross-platform design)
- Uses existing //go:build !unix fallback for telemetry
- Uses go-git for cross-platform git operations
- Build configuration added via .goreleaser.yaml with ZIP format for Windows

## PR Reference
Corresponds to PR #244

Proposed solution

No response

Alternatives or workarounds

No response

[linear]

from evis:

Interesting idea — thanks for writing this up. We've added it to our backlog. We're focused on adding support for more agents right now, but we'll revisit this as capacity opens up.