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/phase0/gguf_head.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""只抓 GGUF 头部（HTTP Range）读元数据，不下载整个文件。
+用法: gguf_head.py <url> [<url> ...]"""
+import sys, struct, urllib.request
+
+TYPES = {0:1,1:1,2:2,3:2,4:4,5:4,6:4,7:1,8:None,9:None,10:8,11:8,12:8}
+NAMES = {0:"u8",1:"i8",2:"u16",3:"i16",4:"u32",5:"i32",6:"f32",7:"bool",8:"str",9:"arr",10:"u64",11:"i64",12:"f64"}
+
+def readstr(b,o):
+    n,=struct.unpack_from("<Q",b,o); o+=8
+    return b[o:o+n].decode("utf-8","replace"), o+n
+
+def peek(url, limit=4_000_000):
+    req=urllib.request.Request(url, headers={"Range":f"bytes=0-{limit}"})
+    b=urllib.request.urlopen(req, timeout=60).read()
+    assert b[:4]==b"GGUF", "not a GGUF"
+    n_kv,=struct.unpack_from("<Q",b,16); o=24
+    out={}
+    for _ in range(n_kv):
+        k,o=readstr(b,o)
+        t,=struct.unpack_from("<I",b,o); o+=4
+        if t==8:
+            v,o=readstr(b,o)
+        elif t==9:
+            et,=struct.unpack_from("<I",b,o); o+=4
+            n,=struct.unpack_from("<Q",b,o); o+=8
+            if et==8:
+                v=[readstr(b,o)[0] for _ in range(min(n,4))]
+                for _ in range(n): _,o=readstr(b,o)
+            else:
+                o+=n*TYPES[et]; v=f"<{n}x{NAMES[et]}>"
+        else:
+            sz=TYPES[t]; v=int.from_bytes(b[o:o+sz],"little",signed=t in (1,3,5,11)); o+=sz
+        out[k]=v
+        if k=="general.architecture":
+            break
+    return out
+
+for url in sys.argv[1:]:
+    print(f"=== {url.split('/resolve/')[0].split('/')[-2] + '/' + url.split('/')[-1]} ===")
+    try:
+        m=peek(url)
+        print("   architecture =", m.get("general.architecture"), "| name =", m.get("general.name"))
+        for k,v in m.items():
+            if "clip" in k or "projector" in k or "audio" in k:
+                print(f"   {k} = {str(v)[:70]}")
+    except Exception as e:
+        print("   ERR", e)