refactor: split core/ui/apps targets and add unit tests

Move all business logic into liblivecaption_core (no Qt dependency) and
the widgets into liblivecaption_ui, leaving two executables: the caption
window and the CLI, which no longer links Qt Widgets. Abstract the ASR
backend behind IAsr so the streaming policy and the live pipeline can be
tested with a scripted fake backend instead of a real model.

把全部业务逻辑下沉到不依赖 Qt 的 liblivecaption_core，界面独立成
liblivecaption_ui，拆出悬浮窗与命令行两个可执行程序（CLI 不再链接 Qt
Widgets）；并用 IAsr 抽象推理后端，使流式策略与实时管线可脱离真模型
用假实现做单元测试。测试还抓到一个真 bug：段恰好结束在 chunk 边界时
只提交了稳定部分，最后几个词被丢掉，已修。

apps/common/appcli.h

@@ -0,0 +1,73 @@
+#pragma once
+
+#include <cstdio>
+#include <string>
+
+#include <QCommandLineOption>
+#include <QCommandLineParser>
+
+#include "qwen3asr.h"
+#include "streamingasr.h"
+
+// 两个可执行程序（GUI / CLI）共用的命令行选项定义与解析。
+namespace lc::app {
+
+inline void addModelOptions(QCommandLineParser & p)
+{
+    p.addOption(QCommandLineOption("model", "主模型 GGUF 路径（架构须为 qwen3vl）", "path"));
+    p.addOption(QCommandLineOption("mmproj", "mmproj GGUF 路径（clip + qwen3a）", "path"));
+    p.addOption(QCommandLineOption("threads", "推理线程数", "n", "8"));
+    p.addOption(QCommandLineOption("max-tokens", "单段最多生成 token 数", "n", "256"));
+    p.addOption(QCommandLineOption("verbose", "输出 llama.cpp/mtmd 的详细日志"));
+}
+
+inline void addStreamOptions(QCommandLineParser & p)
+{
+    p.addOption(QCommandLineOption("stream-chunk", "流式 chunk 秒数", "sec", "2.0"));
+    p.addOption(QCommandLineOption("stream-window", "滑窗上限秒数（仅 window 模式）", "sec", "16"));
+    p.addOption(QCommandLineOption("stream-segment", "单段最长秒数（0=不限）", "sec", "30"));
+    p.addOption(QCommandLineOption("unfixed-tokens", "前缀回滚丢弃的 token 数", "n", "5"));
+    p.addOption(QCommandLineOption("unfixed-chunks", "冷启动不带前缀的 chunk 数", "n", "2"));
+    p.addOption(QCommandLineOption("stream-mode", "流式后端: incremental 或 window", "mode",
+                                   "incremental"));
+}
+
+inline AsrOptions asrOptions(const QCommandLineParser & p)
+{
+    AsrOptions o;
+    o.modelPath = p.value("model").toStdString();
+    o.mmprojPath = p.value("mmproj").toStdString();
+    o.threads   = p.value("threads").toInt();
+    o.maxTokens = p.value("max-tokens").toInt();
+    o.verbose   = p.isSet("verbose");
+    return o;
+}
+
+inline StreamOptions streamOptions(const QCommandLineParser & p)
+{
+    StreamOptions o;
+    o.chunkSec          = p.value("stream-chunk").toDouble();
+    o.windowSec         = p.value("stream-window").toDouble();
+    o.maxUtteranceSec   = p.value("stream-segment").toDouble();
+    o.unfixedTokenNum   = p.value("unfixed-tokens").toInt();
+    o.unfixedChunkNum   = p.value("unfixed-chunks").toInt();
+    o.maxTokensPerStep  = p.value("max-tokens").toInt();
+    o.incremental       = p.value("stream-mode") != QLatin1String("window");
+    return o;
+}
+
+inline bool loadModel(Qwen3Asr & asr, const AsrOptions & opt)
+{
+    if (opt.modelPath.empty() || opt.mmprojPath.empty()) {
+        std::fprintf(stderr, "必须提供 --model 和 --mmproj\n");
+        return false;
+    }
+    std::string err;
+    if (!asr.load(opt, &err)) {
+        std::fprintf(stderr, "加载失败: %s\n", err.c_str());
+        return false;
+    }
+    return true;
+}
+
+} // namespace lc::app