Fix: Use Bun Native Shell for Cross-Platform Windows Support

[Gerkinfeltser]

Problem

Shell commands configured in hooks fail to execute on Windows with error:

bun: command not found: sh

This happens because the plugin uses sh -c ${command} to execute commands, but Bun on Windows doesn't have sh in PATH.

Solution

Use Bun's native cross-platform shell with the ${{ raw: command }} syntax. Bun Shell is a Zig-based interpreter that works natively on Windows, Linux, and macOS without requiring /bin/sh.

Changes

• src/execution/shell.ts: Replace sh -c ${command} with ${{ raw: command }}
• tests/execution.shell.test.ts: Update 4 tests to use cross-platform shell syntax:
  • stderr test: printf 'error' 1>&2 instead of sh -c 'echo >&2'
  • env var test: VAR=val && echo $VAR instead of sh -c
  • quiet mode test: printf 'error' 1>&2 instead of echo 'error' >&2
  • syntax error test: (invalid instead of sh -c 'invalid'

Testing

• ✅ All 24 shell execution tests pass on Windows (Bun 1.3.3)
• ✅ Build succeeds
• ✅ Manual testing on Windows - hooks execute with exitCode=0 and captured output
• ⚠️ Not locally tested on Linux/macOS - However, Bun Shell is explicitly designed to be cross-platform, and all commands used (printf, env var assignment, redirection) are Bun shell builtins that should work identically on all platforms. CI would catch any platform-specific issues.

Known Limitations

During testing, discovered that Bun shell's built-in echo doesn't properly support fd redirection (>&2), but printf does. This is a Bun shell limitation, not specific to this plugin. Users needing to redirect echo output to stderr should use printf instead.