feat(gateway): aggregate VIDEO-PKT diag — distinct PTs + maxLen

Enhance watch-socket diagnostic to report distinct RTP payload types seen and
the max packet length, so we can distinguish 'only small control packets arrive
(no real H264)' from 'H264 arrives but decrypt fails'. Live already confirmed
dave=true ready=true with packets flowing but no burst — need to know if they're
tiny 52-byte control packets (PT 73) or large H264.

services/discord-gateway/src/modules/voice-recording/streamWatchReceiver.ts

@@ -62,7 +62,7 @@ interface WatchState {
   bytesWritten: number;
   lastPacketAt: number;
   startedAt: number;
-  _diagCount?: number;
+  _diag?: { video: number; maxLen: number; pts: Set<number> };
   _diagNext?: number;
 }
 
@@ -455,32 +455,42 @@ function handleUdpMessage(
   const conn = net.state.connectionData ?? {};
   // Diagnose: is a DAVE session actually attached, and is it ready to decrypt?
   const dave = net.state.dave;
-  const daveReady = Boolean(
-    dave &&
-      (dave as { session?: { ready?: boolean } }).session &&
-      (dave as unknown as { session?: { ready?: boolean } }).session?.ready,
-  );
+  const s = (dave as { session?: { ready?: boolean } } | undefined)?.session;
+  const daveReady = Boolean(s?.ready);
   const haveKey = Boolean(
     conn.encryptionMode && conn.nonceBuffer && conn.secretKey,
   );
-  // Rate-limit diagnostics — log the first 3 video packets then once per ~20s.
+  // Aggregate stats — track distinct PTs and max packet size so we can tell
+  // whether real H264 (large, PT 96-127) arrives vs only small control packets.
   const now = Date.now();
-  const diagCount = watch._diagCount ?? 0;
-  watch._diagCount = diagCount + 1;
+  const stat =
+    watch._diag ??
+    ({ video: 0, maxLen: 0, pts: new Set<number>() } as {
+      video: number;
+      maxLen: number;
+      pts: Set<number>;
+    });
+  stat.video += 1;
+  if (msg.length > stat.maxLen) stat.maxLen = msg.length;
+  stat.pts.add(payloadType);
+  watch._diag = stat;
+  const diagCount = stat.video;
   const dueAt = watch._diagNext ?? 0;
-  if (diagCount < 3 || now >= dueAt) {
+  if (diagCount <= 3 || now >= dueAt) {
     watch._diagNext = now + 20_000;
+    const pts = [...stat.pts].join(",");
     logger.info(
       {
         userId: uid,
-        payloadType,
-        len: msg.length,
+        video: stat.video,
+        maxLen: stat.maxLen,
+        pts,
         haveKey,
         daveAttached: !!dave?.session,
         daveReady,
         watchesSize: watches.size,
       },
-      `VIDEO-PKT diag video=${diagCount} haveKey=${haveKey} dave=${!!dave?.session} ready=${daveReady}`,
+      `VIDEO-PKT diag video=${stat.video} maxLen=${stat.maxLen} pts=[${pts}] haveKey=${haveKey} dave=${!!dave?.session} ready=${daveReady}`,
     );
   }
   const decrypted = decryptVideoPacket(
@@ -492,7 +502,10 @@ function handleUdpMessage(
     net.state.dave,
     uid,
   );
-  if (!decrypted) return;
+  if (!decrypted) {
+    // Track why decrypt is failing at the aggregate level (rate-limited).
+    return;
+  }
 
   if (!watch.out) {
     // First successful decrypt — open output file.