style: reformat the repo with oxfmt

[benvinegar]

Summary

• run oxfmt across the repository as a mechanical follow-up to the formatter setup
• reformat source, tests, scripts, docs, examples, and repo config files into one consistent style
• add format:check to main/pr CI so the formatter stays enforced after the initial pass

Verification

• bun run format:check
• bun run typecheck
• bun run check:pack
• HUNK_RUN_TTY_SMOKE=1 bun test test/tty-render-smoke.test.ts -t "split mode renders chrome"
• HUNK_RUN_TTY_SMOKE=1 bun test test/tty-render-smoke.test.ts -t "pager mode hides chrome"

Notes

• this PR is intentionally stacked on top of chore: add oxfmt formatting commands #58
• bun test still hit the pre-existing flaky test/session-cli.test.ts timeouts on fresh main, so I did not use that suite as the main gate for this mechanical formatting pass
• full bun run test:tty-smoke was also flaky in this environment, but the targeted split/pager transcript checks passed