tooling: add pre-commit hook for Prettier format-check on staged files

[fpigeonjr]

Problem

Prettier formatting drift on staged files goes undetected locally and only surfaces in the CI Format-Check step. This causes avoidable CI failures on otherwise-correct commits (most recently #755).

Proposed solution

Add a pre-commit hook that runs Prettier only on staged files using lint-staged + Husky.

This keeps the hook fast (ms per file, not seconds across the whole repo) and catches format issues before they ever reach CI.

Suggested implementation

npm install --save-dev husky lint-staged
npx husky init

.husky/pre-commit

npx lint-staged

package.json addition:

"lint-staged": {
  "**/*.{scss,css,js,json,md}": "prettier --check"
}

Scope

• In scope: Prettier format-check on staged files only
• Out of scope: Running full npm run lint (stylelint across all SCSS) or build:storybook in the pre-commit hook — both are too slow for interactive use

Acceptance criteria

• husky and lint-staged added as devDependencies
• npx husky init sets up .husky/pre-commit
• lint-staged config in package.json runs prettier --check on staged .scss, .css, .js, .json, and .md files
• Committing a Prettier-dirty file is blocked with a clear error message
• npm run lint and npm run compile:check still pass
• prepare script added so npm install auto-installs the hook for new contributors

Related

• fix: resolve max-nesting-depth violations across 3 files #755 (the CI failure that prompted this)
• Add Prettier and format the whole repo #739 (Prettier was added to the repo)