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;

apps/gui/main.cpp

@@ -13,7 +13,9 @@
 #include <QPainter>
 #include <QPixmap>
 #include <QPushButton>
+#include <QStringList>
 #include <QSystemTrayIcon>
+#include <QTabWidget>
 #include <QTimer>
 
 #include "appcli.h"
@@ -66,6 +68,25 @@ bool hasUsableModel()
     return m && ModelStore::isInstalled(*m);
 }
 
+// 后端相关设置的「指纹」：这些值变了就必须重建后端（外观类改动不需要）。
+QString backendKeyOf(const lc::AppSettings & c)
+{
+    return QStringList{ c.modelId,
+                        c.language,
+                        c.captureDevice,
+                        c.modelDir,
+                        c.streamMode,
+                        QString::number(c.chunkSec),
+                        QString::number(c.streamWindowSec),
+                        QString::number(c.streamSegmentSec),
+                        QString::number(c.unfixedTokens),
+                        QString::number(c.unfixedChunks),
+                        QString::number(c.maxTokens),
+                        QString::number(c.threads),
+                        QString::number(c.verbose ? 1 : 0) }
+        .join(QLatin1Char('|'));
+}
+
 } // namespace
 
 int main(int argc, char ** argv)
@@ -95,6 +116,7 @@ int main(int argc, char ** argv)
     parser.addOption(QCommandLineOption("screenshot-delay", "截图前等待秒数", "sec", "6"));
     parser.addOption(QCommandLineOption("no-tray", "不创建托盘图标（测试用）"));
     parser.addOption(QCommandLineOption("screenshot-settings", "打开设置对话框截图后退出", "path"));
+    parser.addOption(QCommandLineOption("settings-tab", "截图设置对话框时先切到某个页签（0-2 或 模型/显示/高级）", "tab"));
     parser.addOption(QCommandLineOption("settings-autoclose", "复现用：自动操作设置对话框（reject|close|accept|ok|apply）", "how"));
     parser.addOption(QCommandLineOption("quit-after", "运行若干秒后优雅退出（测试退出路径用）", "sec"));
     parser.process(app);
@@ -102,12 +124,28 @@ int main(int argc, char ** argv)
     if (parser.isSet("asr-model")) cfg.modelId = parser.value("asr-model");
     if (parser.isSet("language"))  cfg.language = parser.value("language");
     if (parser.isSet("opacity"))   cfg.opacityPercent = parser.value("opacity").toInt();
-    if (parser.isSet("model-dir")) lc::models::ModelStore::setRootOverride(parser.value("model-dir"));
+    if (parser.isSet("model-dir")) cfg.modelDir = parser.value("model-dir");
+    if (!cfg.modelDir.isEmpty()) lc::models::ModelStore::setRootOverride(cfg.modelDir);
 
     // 仅用于验证渲染：打开设置对话框截图后退出
     if (parser.isSet("screenshot-settings")) {
         const QString path = parser.value("screenshot-settings");
         lc::SettingsDialog dlg(!hasUsableModel());
+        // 可选：先切页签，便于给某个页单独截图
+        const QString tab = parser.value("settings-tab");
+        if (!tab.isEmpty()) {
+            if (auto * tw = dlg.findChild<QTabWidget *>()) {
+                bool numeric = false;
+                const int n = tab.toInt(&numeric);
+                if (numeric) {
+                    tw->setCurrentIndex(qBound(0, n, tw->count() - 1));
+                } else {
+                    for (int i = 0; i < tw->count(); ++i) {
+                        if (tw->tabText(i) == tab) { tw->setCurrentIndex(i); break; }
+                    }
+                }
+            }
+        }
         dlg.show();
         QTimer::singleShot(1200, &dlg, [&dlg, path] {
             dlg.grab().save(path);
@@ -173,14 +211,24 @@ int main(int argc, char ** argv)
             return false;
         }
         std::string err;
-        asr = lc::app::makeAsrForModel(*m, cfg.language, cfg.threads,
-                                       parser.isSet("verbose"), &err);
+        asr = lc::app::makeAsrForModel(*m, cfg.language, cfg.threads, cfg.maxTokens,
+                                       cfg.verbose || parser.isSet("verbose"), &err);
         if (!asr) {
             qCritical("加载模型失败: %s", err.c_str());
             return false;
         }
 
+        // 流式参数：只有 llama 后端（Qwen3-ASR）用得到大部分参数，
+        // 流式 ONNX 只关心「更新粒度」。
         lc::StreamOptions sop;
+        sop.windowSec        = cfg.streamWindowSec;
+        sop.maxUtteranceSec  = cfg.streamSegmentSec;
+        sop.unfixedTokenNum  = cfg.unfixedTokens;
+        sop.unfixedChunkNum  = cfg.unfixedChunks;
+        sop.maxTokensPerStep = cfg.maxTokens;
+        sop.incremental      = (cfg.streamMode != QLatin1String("append")
+                                && cfg.streamMode != QLatin1String("window"));
+        sop.appendOnly       = (cfg.streamMode == QLatin1String("append"));
         if (asr->kind() == lc::AsrKind::NativeStreaming) {
             sop.chunkSec = (cfg.chunkSec > 0.0) ? cfg.chunkSec : 0.32;
         } else if (cfg.chunkSec > 0.0) {
@@ -207,28 +255,27 @@ int main(int argc, char ** argv)
         qWarning("采集失败: %s", qUtf8Printable(m));
     });
 
-    // 后端相关项（模型/语言/采集设备）变化才需要重启；外观类改动即时生效
-    const auto backendKey = [&cfg] {
-        return cfg.modelId + QLatin1Char('|') + cfg.language + QLatin1Char('|') + cfg.captureDevice;
-    };
-    QString activeKey = backendKey();
+    // 后端相关项（模型/语言/采集设备/流式参数）变化才需要重启；外观类改动即时生效
+    QString activeKey = backendKeyOf(cfg);
 
     const auto openSettings = [&] {
         lc::SettingsDialog dlg(false);
         QObject::connect(&dlg, &lc::SettingsDialog::settingsApplied, &window, [&] {
+            lc::models::ModelStore::setRootOverride(cfg.modelDir);
             applyAppearance(window, cfg);          // 透明度/字号等立刻可见
-            if (backendKey() != activeKey) {
-                if (startTranscriber()) activeKey = backendKey();
+            if (backendKeyOf(cfg) != activeKey) {
+                if (startTranscriber()) activeKey = backendKeyOf(cfg);
             }
         });
         if (dlg.exec() == QDialog::Accepted) {
+            lc::models::ModelStore::setRootOverride(cfg.modelDir);
             applyAppearance(window, cfg);
-            if (backendKey() != activeKey) {
+            if (backendKeyOf(cfg) != activeKey) {
                 if (!startTranscriber()) {
                     QMessageBox::warning(&window, QObject::tr("启动失败"),
                                          QObject::tr("模型加载失败，请检查设置。"));
                 } else {
-                    activeKey = backendKey();
+                    activeKey = backendKeyOf(cfg);
                 }
             }
         }