[TheGreatAxios]

Closes CL-9381

Summary

• Remove ESLint (eslint, @eslint/js, typescript-eslint) and eslint.config.mjs
• Add oxfmt and oxlint devDependencies, caret ranges like the repo's other devDependencies (the repo had no formatter)
• CI runs format:check after lint
• No lint fixes needed (scripts/generate-exports.mjs, which needed one, is gone in refactor!: replace generated exports with a hand-written barrel #76)
• CONTRIBUTING.md and IMPLEMENTATION.md name oxlint/oxfmt instead of eslint
• Only the lint and format scripts change
• .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 #77. The e2e stack (#67, #68, #70, #71, #62) is based on main and is not below this PR; it re-runs bun run format when it rebases.

Commits

1. build: switch to oxfmt and oxlint: tooling, configs, CI and docs
2. style: format with oxfmt: mechanical reformat only (193 files changed, 4176 insertions(+), 1081 deletions(-)), safe to skip in review