chore(tooling): upgrade Biome to 2.5 (#1575)

## Description

Upgrade Biome from 2.4.16 to 2.5.11 and migrate the recommended-rule configuration to the new preset syntax. Apply the required 2.5 formatter output and replace unsafe optional-chain assertions with failure-preserving matchers.

Closes codemem-jnd6.3.

## Type of Change

- [ ] 🚀 Feature (new functionality)
- [ ] 🐛 Bug fix (fixes an issue)
- [ ] 📚 Documentation (docs-only change)
- [x] 🔧 Maintenance (refactor, chore, CI, etc.)
- [ ] 🧪 Testing (test-only changes)

## Testing

- [x] Relevant checks pass locally (`pnpm run tsc`, `pnpm run lint`, `pnpm run test`)
- [ ] Added/updated tests for changes
- [x] Manually verified changes work as expected

Additional checks: full `pnpm run check` (5,740 tests), focused UI assertion test, and Snyk high-severity SCA scan.

## Checklist

- [x] Code follows project style (`pnpm run lint` passes for touched files)
- [x] Self-review completed
- [x] Documentation updated (not needed)
- [x] No new warnings introduced