fix(i18n): refine Chinese prose and prompt validation

scripts/translation-prompt.spec.ts

@@ -40,6 +40,15 @@ describe('translation prompt rendering', () => {
       terminology: 'terms',
     })).toThrow('does not match source language Chinese')
   })
+
+  it('rejects malformed template placeholders before injecting rule contents', () => {
+    expect(() => renderTranslationPrompt(document.replace('{{source_lang}}', '{{source-lang}}'), {
+      sourceLanguage: 'English',
+      sourceFilename: 'guide.md',
+      translationRules: 'A literal {{source_lang}} in injected rules.',
+      terminology: '| English | 中文 |',
+    })).toThrow('template contains malformed placeholder syntax')
+  })
 })
 
 describe('translation response XML', () => {

scripts/translation-prompt.ts

@@ -82,6 +82,10 @@ export function renderTranslationPrompt(document: string, input: TranslationProm
     source_filename_zh: sourceFilenameZh,
   }
   const template = extractTranslationPrompt(document)
+  const placeholderFreeTemplate = template.replace(PLACEHOLDER, '')
+  if (placeholderFreeTemplate.includes('{{') || placeholderFreeTemplate.includes('}}')) {
+    throw new Error('translation prompt: template contains malformed placeholder syntax')
+  }
   const names = [...template.matchAll(PLACEHOLDER)].map(match => match[1] ?? '')
   const unknown = names.filter(name => !TRANSLATION_PROMPT_PLACEHOLDERS.includes(name as TranslationPromptPlaceholder))
   if (unknown.length > 0) throw new Error(`translation prompt: unsupported placeholder(s): ${[...new Set(unknown)].join(', ')}`)

scripts/verify-translation-prompt.ts

@@ -37,7 +37,6 @@ try {
     translationRules,
     terminology,
   })
-  if (englishSource.includes('{{') || chineseSource.includes('{{')) throw new Error('rendered prompt contains an unresolved placeholder')
   if (!englishSource.includes('[English](example.md) | 中文')) throw new Error('English-source render does not carry the Chinese switcher instruction')
   if (!chineseSource.includes('English | [中文](example.zh.md)')) throw new Error('Chinese-source render does not carry the English switcher instruction')