[Issue-6] (feat) Add deterministic command checks

[dbrosio3]

Summary

• expands the v2 tool schema with timeout, mode, run, and fail-fast settings
• adds deterministic command execution to pushgate pre-push with safe {changed_files} argv expansion
• bundles the TypeScript runner into the installer-friendly bin/pushgate.mjs
• updates docs/templates and adds config, runner, and installed-hook integration coverage

Validation

• pnpm test
• pnpm run build
• pnpm run check:shell
• git diff --check

Closes #6