fix: replace hand-assembled Opus probe blob with real ffmpeg/libopus output

Previous probe sample had invalid Ogg page CRC32s, so Chrome/Firefox rejected it and the capability check always returned false. New 176-byte libopus sample has verified-correct CRCs. Adds structural-validity tests.

DeepDrftPublic/Interop/audio/OpusCapability.ts

@@ -18,15 +18,22 @@
  */
 
 /**
- * A minimal, valid Ogg-Opus file: an OpusHead page, an OpusTags page, and one audio page carrying a
- * single 20 ms silence packet (mono, 48 kHz). Base64-encoded; ~250 bytes decoded. This is the
- * smallest blob a conformant decoder will accept and a non-supporting decoder will reject, which is
- * exactly the discriminator we need.
+ * A minimal, valid Ogg-Opus file generated by ffmpeg/libopus (libopus via Lavc62, libavformat62).
+ * Three pages: OpusHead (page 0), OpusTags (page 1), one audio page of ~50 ms silence (page 2,
+ * EOS flag set). Mono, 48 kHz. All three Ogg page CRC32s are verified correct — generated by
+ * construction; not hand-assembled.
+ *
+ * ffmpeg command:
+ *   /c/ffmpeg/ffmpeg.exe -f lavfi -i anullsrc=r=48000:cl=mono -t 0.05 \
+ *     -c:a libopus -b:a 24k -f ogg /tmp/opusprobe.opus
+ *
+ * 176 bytes decoded; 236 chars base64.
  */
 const PROBE_OGG_OPUS_BASE64 =
-    'T2dnUwACAAAAAAAAAACRYwAAAAAAANieBHsBE09wdXNIZWFkAQEAAIC7AAAAAABPZ2dTAAAAAAAA' +
-    'AAAAAJFjAAABAAAAUkOcUAEMT3B1c1RhZ3MAAAAAAAAAAE9nZ1MABABAAQAAAAAAkWMAAAIAAABU' +
-    '/9D/A2P4//////////////////////////////////////////////////////////////////8=';
+    'T2dnUwACAAAAAAAAAAD/3cwSAAAAAJGmJikBE09wdXNIZWFkAQE4AYC7AAAAAABPZ2dTAAAA' +
+    'AAAAAAAAAP/dzBIBAAAA6iGxjgE+T3B1c1RhZ3MNAAAATGF2ZjYyLjEyLjEwMQEAAAAdAAAA' +
+    'ZW5jb2Rlcj1MYXZjNjIuMjguMTAxIGxpYm9wdXNPZ2dTAASYCgAAAAAAAP/dzBICAAAAjUsr' +
+    'kAMDAwP4//74//74//4=';
 
 let cachedSupport: Promise<boolean> | null = null;