[Blankll]

Follow-up on the review of #542 (zh-TW).

Fix: language choice was never persisted

getStoredLocale() read localStorage['lang'], which nothing in the codebase ever wrote — so a language picked in settings silently reverted to OS auto-detection on the next launch. This was pre-existing (affected zhCN too); for zh-TW users it was masked because auto-detection now happens to resolve to zhTW.

getStoredLocale() now:

1. validates the lang value (previously cast unchecked),
2. falls back to the pinia-persisted app.languageType (pinia-plugin-persistedstate default key = store id, verified from the plugin source), so existing users' past choices take effect retroactively — no picker change needed,
3. degrades gracefully to auto-detection on a corrupted blob.

Tests

• tests/lang/zhTW.test.ts merged into tests/lang/parity.test.ts: key parity + placeholder checks are now parametrized over zhCN / zhTW, and both get two-direction assertions (en→locale and locale→en no-extra-keys) — stronger than the previous zhCN one-direction check. Adding a future locale is one array entry.
• tests/lang/index.test.ts extended with the behavior feat(i18n): add Traditional Chinese (zh-TW) #542 introduced but didn't cover: it.each over zh-TW / zh-Hant-TW / zh-Hant / zh-HK / zh-MO → cn, bare zh / en-US → en, plus the three persistence-fallback paths (valid zhTW, invalid value, corrupted JSON).

Verification

• npx jest — 70 suites / 1983 tests pass
• npx tsc --noEmit — clean
• npx eslint on changed files — clean

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.89%. Comparing base (c112325) to head (bbd6958).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #544      +/-   ##
==========================================
+ Coverage   71.88%   71.89%   +0.01%     
==========================================
  Files         169      169              
  Lines       29735    29743       +8     
  Branches     1479     1482       +3     
==========================================
+ Hits        21376    21385       +9     
  Misses       7909     7909              
+ Partials      450      449       -1     

Files with missing lines	Coverage Δ
src/lang/index.ts	100.00% <100.00%> (+5.00%)	⬆️

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