chore: adopt Biome for linting and formatting

[kjellbergzoey]

Summary

Adopts Biome as the single tool for linting and formatting.

• Adds @biomejs/biome as a devDependency and a biome.json configured for this project: TypeScript + JSX/Ink React, 2-space indentation, single quotes, ES modules, recommended linter rules, and organize-imports (Biome 2.x assist action).
• Adds npm scripts: lint (biome check .) and format (biome check --write .).
• Adds a dedicated, fast lint job to CI (single Node version) that runs before/alongside the existing test matrix.

About the large diff

The bulk of this PR is the one-time biome check --write . format pass applied across the whole repo. This is expected for an "adopt Biome" change. There are no behavioral changes — only formatting and import ordering.

After applying, npm run typecheck, npm test (70 passing), and npm run build all remain green.

A note on disabled rules

A few recommended lint rules are disabled in biome.json because they conflict with the project's existing strict tsconfig or React/Ink patterns:

• noNonNullAssertion and useLiteralKeys — clash with noUncheckedIndexedAccess / noPropertyAccessFromIndexSignature from @sindresorhus/tsconfig; their autofixes would break typecheck.
• useExhaustiveDependencies and noArrayIndexKey — would require behavioral refactors of Ink components, out of scope for a formatting PR.

These can be revisited in follow-ups if desired.

🤖 Generated with Claude Code

[kjellbergzoey]

Rebased onto current main (after #11–#16 merged) to clear the conflicts. The Biome format pass was regenerated on top of the latest code rather than hand-resolving the 47-file diff, so the result is deterministic.

Now green end-to-end: npm run lint clean (62 files), npm run typecheck, npm test (111 passed), npm run build all pass. Two small lint fixes beyond pure formatting: string-concat → template literal in db/list.tsx, and an empty destructure pattern in wp.tsx. Ready to merge. 🤖