Add correction layer to i18n that allows for corrections where the official translation is wrong

docs/I18N.md

@@ -156,6 +156,11 @@ rebuilt.
   the source on the record's own ids, then the 下半 season (`act2autochess`). Rich-text tags and placeholders are the
   same as in Chinese, so `ui/richText.js` renders the English unchanged (a few official EN texts leave a tag unclosed;
   the parser runs it to the end of the text, as the game does).
+- **Corrections**: `tools/i18n/corrections-<lang>.json` (the pack's code: `en`, `ja`, `ko`, `zh-TW`; optional) is
+  tried before the official data of that language, for an official translation that contradicts the Chinese text and
+  the engine (exact match on the raw Chinese text; the plain twin is stripped from it; every entry carries a `_why:`
+  note; `_`-keys are never written to the overlay). Only `corrections-en.json` exists. Counted as `correction` in the
+  coverage report.
 - **Fallbacks**, in order: `tools/i18n/fallback-remake.json` (the remake's own strings: stage-name parts, item notes,
   the escaped levels' map names, the season name), `tools/i18n/fallback-pr70.json` (PR #70's translations of texts the EN client
   lacks: modules of CN-only operators, the 甄选 slots, 结算称号 criteria, emote labels), then `public/i18n/en.json`;