Fix trace command cwd handling on Windows

[mysubb01]

Summary

• remove the inline cd ...; wrapper from the trace command
• run the configured trace command with spawn using cwd instead
• add shell quoting helpers and tests for Windows/POSIX trace directory substitution

Why

This addresses #48. On Windows, cd without /d cannot switch drives, so a project on P: launched from a storage path on C: fails before tsc --generateTrace runs. Passing the project path through spawn({ cwd }) avoids embedding a drive-changing cd in the shell command.

Verification

• pnpm lint
• pnpm typecheck
• pnpm exec vitest run
• pnpm build