fix(i18n): keep the baseline intact on failed updates and strict audits

`--update-baseline` now writes nothing while any locale is unreadable or
has missing or extra keys, so an incomplete translation cannot reshape
the baseline. `--fail-on-identical` no longer reads the baseline it
ignores, so a damaged file cannot block a strict audit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/validation-map.md

@@ -260,7 +260,8 @@ text changes, so copying reworded English into a locale fails as well.
 Baseline entries that are no longer English-identical (translated, removed, or
 reworded) are reported but do not fail. `pnpm run i18n:baseline:update`
 rewrites the baseline from the current locale files, dropping those entries
-and printing every added one. Run it only after translating, or for a value
+and printing every added one; it writes nothing while any locale is unreadable
+or has missing or extra keys. Run it only after translating, or for a value
 that is legitimately identical in that language; review the diff, and never
 run it in CI. A new locale starts with no baseline entries, so it has to
 record its legitimate identical values the same way.

tools/i18n/check-drift.mjs

@@ -269,7 +269,8 @@ export function run({
         enLeaves = collectLeaves(
             readJson(resolve(i18nDir, `${EN_LOCALE}.json`))
         );
-        baseline = readBaseline(baselinePath);
+        // A strict audit ignores the baseline, so a damaged file cannot block it.
+        baseline = strict ? new Map() : readBaseline(baselinePath);
     } catch (error) {
         if (!enLeaves || !update) {
             log(`FAIL ${formatError(error)}`);
@@ -283,7 +284,6 @@ export function run({
     const identicalByLocale = new Map();
     const rejected = [];
     let failed = false;
-    let unreadable = false;
     let staleTotal = 0;
 
     for (const locale of locales) {
@@ -292,7 +292,7 @@ export function run({
         try {
             result = checkLocale({ i18nDir, locale, enLeaves, baseline, mode });
         } catch (error) {
-            failed = unreadable = true;
+            failed = true;
             log(`FAIL ${file}: ${formatError(error)}`);
             continue;
         }
@@ -318,8 +318,11 @@ export function run({
     reportRejected(log, rejected, enLeaves, mode);
 
     if (update) {
-        if (unreadable) {
-            log('FAIL baseline not written: a locale file could not be read.');
+        // Only a complete, readable set of locales is a state worth recording.
+        if (failed) {
+            log(
+                'FAIL baseline not written: fix the unreadable, missing or extra keys above first.'
+            );
             return 1;
         }
         writeBaseline(log, baselinePath, baseline, identicalByLocale);

tools/i18n/check-drift.test.mjs

@@ -214,6 +214,36 @@ test('--update-baseline keeps the old baseline when a locale is unreadable', ()
     assert.deepEqual(readBaselineFile(), { de: { PIN: 'PIN' } });
 });
 
+test('--update-baseline keeps the old baseline while keys are missing or extra', () => {
+    writeLocale('en', EN);
+    writeLocale('de', { APP: { TITLE: 'IPTVnator', OLD: 'Alt' }, PIN: 'PIN' });
+    writeBaseline({ de: { 'APP.SAVE': 'Save', PIN: 'PIN' } });
+
+    const { code, output } = check('--update-baseline');
+
+    assert.equal(code, 1);
+    assert.match(output, /baseline not written/);
+    assert.deepEqual(readBaselineFile(), {
+        de: { 'APP.SAVE': 'Save', PIN: 'PIN' },
+    });
+});
+
+test('--fail-on-identical audits even when the baseline is damaged', () => {
+    writeLocale('en', EN);
+    writeLocale('de', {
+        APP: { TITLE: 'IPTVnator', SAVE: 'Speichern' },
+        PIN: 'PIN-Code',
+    });
+    writeFileSync(baselinePath, '{ broken');
+
+    const { code, output } = check('--fail-on-identical');
+
+    assert.equal(code, 1);
+    assert.match(output, /^FAIL de\.json: missing=0 extra=0 identical_en=1$/m);
+    assert.match(output, /de\.json APP\.TITLE: "IPTVnator"/);
+    assert.equal(check().code, 1);
+});
+
 test('rejects unknown and conflicting flags', () => {
     writeLocale('en', EN);