fix: run traces from the workspace cwd on Windows

[yichensunjoe]

Fixes #48.

Summary

• stop wrapping the trace command in an inline (cd ...) shell snippet
• run the configured trace command from the selected workspace/project cwd instead
• quote the generated trace directory with shell-aware rules so cmd.exe and POSIX shells both work
• add unit coverage for Windows default-shell, bash-on-Windows, POSIX escaping, and shell fallback behavior

Validation

• pnpm exec eslint src/commands.ts src/shell.ts test/index.test.ts
• pnpm exec vitest run test/index.test.ts
• pnpm typecheck
• pnpm build