fix(goLive): encode H264 baseline to match SDP profile-level-id (black tile)

SDP offer advertises profile-level-id=42e01f (constrained baseline) but
x264 encoded the default High profile — Discord's receiver configures its
decoder from the negotiated profile, so the High-profile bitstream failed
to decode → black GoLive tile despite valid access units + correct RTP
timestamps (fixed in 42a503c).

- Add -profile:v baseline to H264 encoder options (matches @dank074's
  proven config; SPS now 6742c01e → profile_idc=66 baseline, aligns with
  the 42e01f fmtp).
- Default x264 tune film → zerolatency (no lookahead — correct for live
  GoLive; @dank074 uses it).
- Update goLive-port test to assert baseline + zerolatency.

services/discord-gateway/tests/goLive-port.test.ts

@@ -22,11 +22,14 @@ describe("goLive port: codec + encoders", () => {
     expect(normalizeVideoCodec("av1")).toBe("AV1");
   });
 
-  it("software encoder exposes x264 libx264 superfast film", () => {
+  it("software encoder exposes x264 libx264 baseline zerolatency", () => {
     const enc = Encoders.software()();
     expect(enc.H264.name).toBe("libx264");
     expect(enc.H264.options).toContain("-preset superfast");
-    expect(enc.H264.options).toContain("-tune film");
+    expect(enc.H264.options).toContain("-tune zerolatency");
+    // Baseline profile is REQUIRED to match the SDP's profile-level-id=42e01f
+    // (constrained baseline) — High-profile bitstreams fail to decode → black
+    expect(enc.H264.options).toContain("-profile:v baseline");
   });
 
   it("CodecPayloadType has opus + H264 entries", () => {