[Prodyte]

Closes #1

Built by the ship workflow: dev, reviewer and qa agents in GitHub Actions. This PR was opened by hand after the run, because the workflow wasn't allowed to create PRs yet (now fixed).

• Button: sun/moon icon button beside the account button in the phone top bar, and in the navigation on wider screens. Label reads "Switch to dark theme" or "Switch to light theme".
• Behaviour: flips to the opposite of what is showing; on System it switches away from the OS theme. Saves to nihongo.theme, the same setting as Settings → Theme. Only Settings returns to System.
• Settings sync: App holds the theme, so the Settings dropdown follows the toggle.
• Focus ring: reuses the account-button classes, so the global button:focus-visible outline applies.
• Lessons: lives in the existing top bar and nav, so it's hidden during full-screen lessons.
• 320px: below 22rem the 日本語 label beside the logo is hidden so the bar fits on one row. This is a CSS estimate; no browser rendered it, so check on a phone before merging.

Round	Reviewer	QA
1	CHANGES (top bar likely wraps at 320px)	PASS
2	APPROVE	PASS

Tests: 428 passed, 1 skipped.

Run log: https://github.com/Prodyte/nihongo/actions/runs/38344650864

[Prodyte]

@claude The theme toggle has an aria-label but no tooltip. Add a title with the same text ("Switch to dark theme" / "Switch to light theme") so mouse users see what it does on hover, and cover it in the toggle's tests.

[github-actions]

Claude finished @Prodyte's task in 1m 58s —— View job

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Theme toggle tooltip added

• Read the request and the toggle code
• Add title matching the aria-label (dev)
• Cover it in the toggle's tests (qa)
• Review and QA in parallel
• Commit and push

The toggle in src/App.tsx now sets title to the same text as its aria-label ("Switch to dark theme" / "Switch to light theme"). The label is computed once and used for both. In src/ThemeToggle.test.tsx, every label check now asserts title as well as aria-label. That covers both states, before and after a click, plus the reload, invalid-stored-theme and Settings-sync tests.

The full suite passed: 428 passed, 1 skipped. Pushed as 3323e24.

Round	Reviewer	QA
1	APPROVE	PASS
· branch ship/issue-1