chore: remove packages/tools and unused oxfmt/oxlint dependencies

[kazupon]

Summary

- Add pnpm install to just init so that Node.js dependencies (e.g. oxfmt, oxlint) are installed during setup
- Add pnpm oxlint to just lint to run JS/TS linting alongside Clippy

Without pnpm install in init, just ready fails because oxfmt (called by just fmt) is not available.

• Remove packages/tools directory — all test utilities were ported to the Rust binary vtt in Port packages/tools bins to single Rust binary (vtt) #291, leaving this package with only oxfmt/oxlint dependencies and no source code
• Move oxfmt/oxlint/oxlint-tsgolint dependencies to root package.json (there is no production JS/TS code to lint/format, but they are kept for lint-staged pre-commit hooks)
• Remove cross-env dependency (no longer needed after vtt migration)
• Remove pnpm oxfmt from just fmt (moved to lint-staged only)
• Remove packages/tools from pnpm-workspace.yaml

[kazupon]

I've just noticed that packages/tools is not used.
It seems there’s no longer much point in installing oxlint or oxfmt for this project. 🤔

[kazupon]

I've just updated this PR

[branchseer]

packages/tools is needed by fspy tests

[kazupon]

Thank you for your advice.
I've just understood about it.
I'll close this PR