Add TypeScript type checking to pre-commit or CI #1202

Problem

TypeScript type errors in the frontend can slip through to CI/Netlify builds because there is no local type checking step. The current .pre-commit-config.yaml excludes ui/ entirely (line 1: exclude: "^docs/|/migrations/|ui/"), and we only run prettier formatting checks in CI, not tsc.

This was exposed in PR #1198 where a type mismatch (null added to one interface but not a dependent one) passed local commits and was only caught by the Netlify build.

Proposal

Add tsc --noEmit as a check that runs before code reaches CI. Three approaches, from simplest to fastest:

Option A: pre-commit hook (repo: local)

# .pre-commit-config.yaml
- repo: local
  hooks:
    - id: ui-typecheck
      name: TypeScript type check
      entry: bash -c 'cd ui && npx tsc --noEmit'
      language: system
      files: ^ui/.*\.(ts|tsx)$
      pass_filenames: false

• Adds ~10s to commits touching TS files
• Uses files: pattern to bypass the global exclude: ui/ rule
• pass_filenames: false because tsc --noEmit must check the whole project (type errors can cascade across files)

Option B: Husky + lint-staged

// ui/package.json
"lint-staged": {
  "*.{ts,tsx}": ["bash -c 'tsc --noEmit'"]
}

With Husky managing the git hook from the ui/ directory. This is more standard for JS/TS projects and keeps frontend tooling self-contained, but adds another hook manager alongside pre-commit.

Option C: CI-only check (fastest local workflow)

Add tsc --noEmit as a step in the GitHub Actions / Netlify CI pipeline, separate from the build. Catches errors before deploy without slowing local commits. Downside: errors are caught later in the feedback loop.

Notes

• tsc --noEmit cannot meaningfully check a subset of files — TypeScript's type system is whole-program, so a change in file A can cause errors in file B through imported types
• Current tsc --noEmit takes ~10s on this project
• The existing Netlify build already catches these errors, but the feedback loop is slow (~2-3 min)