feat(gui): expose the streaming and debug options in the advanced page

These were command-line only. Add them to the settings dialog so the whole
feature set is reachable without arguments: stream mode, window limit,
segment limit, prefix-rollback token count, cold-start chunk count, max
tokens per step, thread count, verbose logging and the model directory. The
streaming group is grouped and greyed out for streaming-ONNX models, which
only use the commit granularity. The backend fingerprint now includes them,
so changing one restarts the recogniser; appearance changes still apply live.

Also add a test-only --settings-tab so a specific page can be screenshotted.

设置「高级」页补上原来只有命令行才有的选项：流式策略/滑窗上限/单段最长/前缀回滚
token 数/冷启动 chunk 数/单段最多生成 token/线程数/详细日志/模型目录。流式那一组
单独成组，选了流式 ONNX 模型时置灰（它们只用「更新粒度」）。这些值纳入「后端指纹」，
改动会重启识别后端；外观类改动仍然即时生效。另加测试用 --settings-tab 以便给单个
页签截图。

apps/common/appcli.h

@@ -109,7 +109,7 @@ inline void addBackendOptions(QCommandLineParser & p)
 // 按注册表里的模型直接构造后端（GUI 用；不依赖任何命令行参数）
 inline std::unique_ptr<IAsr> makeAsrForModel(const models::ModelInfo & m,
                                              const QString & language,
-                                             int threads, bool verbose,
+                                             int threads, int maxTokens, bool verbose,
                                              std::string * err)
 {
     QStringList missing;
@@ -125,6 +125,7 @@ inline std::unique_ptr<IAsr> makeAsrForModel(const models::ModelInfo & m,
         o.modelPath  = m.filePath(QStringLiteral("model")).toStdString();
         o.mmprojPath = m.filePath(QStringLiteral("mmproj")).toStdString();
         o.threads    = threads;
+        if (maxTokens > 0) o.maxTokens = maxTokens;
         o.verbose    = verbose;
         auto a = std::make_unique<Qwen3Asr>();
         if (!a->load(o, err)) return nullptr;