build: switch to oxfmt and oxlint

[TheGreatAxios]

Closes CL-9370

Summary

• Add oxfmt and oxlint as exact-pinned devDependencies (the repo had no formatter or linter)
• Run lint and format:check in CI after install
• Remove two unused type imports in src/client/client.ts (no-unused-vars)
• Replace new Array<T>(n) with Array.from<T>({ length: n }) in src/tools/create-tools.ts (unicorn/no-new-array)
• .oxfmtrc.json sets printWidth: 80 (Prettier's width); everything else is oxfmt's defaults, including sorting package.json keys
• .oxlintrc.json turns the correctness category from warn to error; no rules are disabled
• lint runs oxlint, format runs oxfmt, format:check runs oxfmt --check

Stacked on #8.

Commits

1. build: switch to oxfmt and oxlint: tooling, configs and lint fixes
2. style: format with oxfmt: mechanical reformat only (15 files changed, 629 insertions(+), 299 deletions(-)), safe to skip in review