feat: add real-time caption CLI prototype with Qwen3-ASR

Add a C++/Qt6/CMake CLI prototype that captures the default sink
monitor through libpulse and transcribes it in-process with Qwen3-ASR
via libllama/libmtmd. Add phase 0/1 verification docs.

新增实时字幕命令行原型：libpulse 采集默认输出 monitor，进程内用
libllama/libmtmd 跑 Qwen3-ASR 推理。附阶段 0/1 验证文档。

experiments/phase1/live_test.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Phase 1 实机验证：实时采集默认输出 + 转写
+set -uo pipefail
+BIN=/home/blumia/Sources/live-caption/build/live-caption-cli
+M=${M:-/tmp/opencode/models/Qwen3-ASR-0.6B-Q8_0.gguf}
+MM=${MM:-/tmp/opencode/models/mmproj-Qwen3-ASR-0.6B-Q8_0.gguf}
+PLAY=${PLAY:-/tmp/opencode/samples/play_48k.wav}
+LOG=/tmp/opencode/live.log
+ERR=/tmp/opencode/live.err
+TIMEOUT=${TIMEOUT:-60}
+
+"$BIN" --model "$M" --mmproj "$MM" --threads 8 > "$LOG" 2> "$ERR" &
+PID=$!
+echo "live-caption-cli pid=$PID, 等待模型加载..."
+sleep 4
+
+echo "开始播放: $PLAY"
+paplay --device="$(pactl get-default-sink)" "$PLAY"
+
+echo "播放结束，等 4s 让最后一段收尾..."
+sleep 4
+kill "$PID" 2>/dev/null
+wait "$PID" 2>/dev/null
+
+echo "================ 实时输出 ================"
+tr '\r' '\n' < "$LOG" | grep -vE '^\s*$' | sed 's/\x1b\[[0-9;]*m//g'
+echo
+echo "================ 每次推理耗时 ================"
+grep '\[infer\]' "$ERR" || true