Revert "翻译兜底引擎与摘要A/B解耦:固定 gemma4-e2b(日语强项+本机已验证),不再寄生 useMinicpm5(纪要方向的开关;MiniCPM5日语未标定、本工程纪要场景日语表现差);新增 fallbackModelDirName/GgufName/ChatTemplate 三常量,translateFallback 改用;摘要管线维持原开关不动"

This reverts commit d18554d731.

app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt

@@ -314,12 +314,6 @@ class MainActivity : AppCompatActivity() {
                 else "gemma-4-E2B_q4_0-it.gguf"
     private val summarizeChatTemplate: String
         get() = if (useMinicpm5) "minicpm" else "gemma4"
-    // 翻译兜底引擎(2026-09-16 用户拍板与摘要 A/B 解耦):固定 E2B——日语强项、
-    // 本机已验证(9/11 纪要首跑);不再寄生 useMinicpm5(那只是纪要方向的决定,
-    // MiniCPM5 日语未标定且本工程纪要场景对日语表现差)
-    private val fallbackModelDirName = "gemma4-e2b"
-    private val fallbackGgufName = "gemma-4-E2B_q4_0-it.gguf"
-    private val fallbackChatTemplate = "gemma4"
     private lateinit var summarizeButton: Button
     private lateinit var copyMinutesButton: Button
     private lateinit var minutesStatus: TextView
@@ -2381,8 +2375,8 @@ class MainActivity : AppCompatActivity() {
             Log.i(TAG, "TAP-FALLBACK sid=$sid skipped=budget")
             return null
         }
-        val gguf = File(File(externalModelDir, fallbackModelDirName),
-            fallbackGgufName)
+        val gguf = File(File(externalModelDir, summarizeModelDirName),
+            summarizeGgufName)
         if (!gguf.isFile) {
             Log.i(TAG, "TAP-FALLBACK sid=$sid skipped=no-model " +
                     gguf.absolutePath)
@@ -2397,7 +2391,7 @@ class MainActivity : AppCompatActivity() {
         return try {
             e = LlmEngine(gguf.absolutePath, SUMMARY_CTX,
                 if (isRecording) SUMMARY_THREADS_BUSY else SUMMARY_THREADS,
-                chatTemplate = fallbackChatTemplate)
+                chatTemplate = summarizeChatTemplate)
             val out = e.generate(
                 systemPrompt = "你是专业翻译。把给出的句子翻译成" + transTargetName() +
                         "。只输出译文本身,不要解释、不要引号、不要抄写原文," +