The changeset parser hard-fails on fragments without a `pr:` field.
Closes#3102 (changeset schema violation identified in review).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Address adversarial review feedback on PR #3102:
1. shell:true is now conditional (process.platform === 'win32')
- POSIX path unchanged: no shell spawn, no overhead, original
signal/exit-code semantics and windowsHide effect preserved
- Windows path: still routes through cmd.exe to resolve npm.cmd
via PATHEXT (the actual fix for ENOENT)
2. Added .changeset/windows-npm-shell-fix.md (Fixed type)
Reviewed feedback resolved:
- Cross-platform regression risk → shell now Windows-only
- Missing changeset → added
