Windows support (PowerShell)

[guohai]

Summary

atem currently ships for Linux and macOS (x64 + arm64). This issue tracks Windows support, so atem runs natively in PowerShell.

Motivation

Windows is a large share of developer desktops. Right now Windows users have no native path — only WSL. First-class Windows support widens atem's reach considerably.

Scope

• Build target — add x86_64-pc-windows-msvc to the release matrix in .github/workflows/release.yml.
• PTY layer — claude_client.rs / codex_client.rs use portable-pty, which supports Windows ConPTY. Needs verification and likely some conditional handling.
• Paths & config — ~/.config/atem/ resolution via the dirs crate already maps to %APPDATA% on Windows; audit assumptions about path separators and home dir.
• Process spawning — serv daemons re-exec themselves; the detach pattern (stdin(null), file-redirected stdout/stderr) needs a Windows equivalent.
• Terminal / TUI — crossterm + ratatui are cross-platform; verify rendering and key handling under Windows Terminal + legacy conhost.
• Install — a PowerShell install script (install.ps1) alongside the existing install.sh, plus the npm wrapper's os/cpu fields.

Good to know

• This is help wanted — ideally owned by someone who develops on Windows day to day, since it needs real testing on the platform, not just CI.
• Suggested approach: get a CI build green first (proves it compiles + links), then work through the runtime surfaces above one at a time.

Not in scope

• ARM Windows — defer until x64 works.

Part of the atem roadmap.