mux: sink and reader audit fixes; DTS in MP4; halt-aware network receive

Fixes from the mkv, mp4, network and ts sink audit; track timing and
DiscardPadding ride the FMKV wire. MP4 writes DTS per ETSI TS 102 114
(ddts rates and timescales). The MKV PCM depth probe is bounded and
evidence-based. Network receives use keepalive and wait on readiness,
so a Stop or a dead peer ends them.

Cargo.lock

@@ -328,9 +328,11 @@ dependencies = [
  "memchr",
  "rayon",
  "roxmltree",
+ "rustix",
  "serde",
  "serde_json",
  "sha1",
+ "socket2",
  "tempfile",
  "tracing",
  "zip",
@@ -626,6 +628,16 @@ version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b9be42f50aa861c555654aa3a37f52f4b1074bacf4e48fe0ef7fa584e80f1f0f"
 
+[[package]]
+name = "socket2"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3d1e2c7f27f8d4cb10542a02c49005dbd6e93095799d6f3be745fae9f8fedd4"
+dependencies = [
+ "libc",
+ "windows-sys",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.119"