fix(header): complete atom review

[egdev6]

Summary

Completes the Header atom review checklist.

Closes #128

Type of change

• 🧩 New component
• 🐛 Bug fix
• 🎨 Design tokens
• ♿ Accessibility
• 🏗️ Infrastructure
• 📚 Documentation

Component checklist (skip if not applicable)

• Follows the 5-file structure (types.ts, use*.ts, Component.tsx, index.ts, *.stories.tsx)
• CVA variants defined in types.ts, not inline
• No hardcoded colors — uses tokens from theme.css
• No any types — TypeScript strict
• ARIA attributes present and correct
• Keyboard navigable (Tab, Enter, Escape where applicable)
• Dark mode works correctly
• Storybook stories cover: default, variants, states (hover, focus, disabled)
• Tests added or updated

How to test

1. pnpm test -- src/components/atoms/header/Header.test.tsx
2. pnpm exec biome check src/components/atoms/header
3. pnpm exec tsc --noEmit
4. pnpm run storybook-build
5. Open Storybook and verify Header stories for semantic tags, visual sizes, sr-only, id, and custom tone.

Screenshots / recordings (if applicable)

Not included.

Notes for reviewer

• Fixes the previous class composition bug where a requested heading size could also receive the default fs-h1 class.
• tag controls semantic heading level. size controls visual scale. fontSize remains supported as a backwards-compatible alias for size.
• Header is non-interactive, so keyboard behavior is native/not applicable beyond standard heading semantics.

[Copilot]

Pull request overview

Completes the Header atom review by moving it to named exports, separating semantic heading level from visual size, and adding tests/stories for the updated API.

Changes:

• Adds size as the visual heading scale while keeping fontSize as a compatibility alias.
• Updates Header exports, hook logic, variants, Storybook stories, and tests.
• Expands Header props to include native heading attributes.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/components/atoms/header/types.ts	Updates CVA variants, Header prop types, and size/font aliases.
src/components/atoms/header/useHeader.ts	Resolves semantic tag and visual size into rendered props/classes.
src/components/atoms/header/Header.tsx	Converts Header to a named export and renders the resolved tag.
src/components/atoms/header/index.ts	Updates the barrel export to use the named Header export.
src/components/atoms/header/Header.test.tsx	Adds unit tests for default semantics, sizing, alias behavior, IDs, and sr-only headings.
src/components/atoms/header/Header.stories.tsx	Refreshes stories to document semantic tags, visual sizes, fonts, sr-only, IDs, and custom tone.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.