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.toml

@@ -48,6 +48,8 @@ rip = [
     "dep:crossbeam-channel",
     "dep:rayon",
     "dep:memchr",
+    "dep:socket2",
+    "dep:rustix",
 ]
 
 [dependencies]
@@ -62,6 +64,12 @@ aes = { version = "0.9", optional = true }
 freemkv-unlock = { path = "../freemkv-unlock", optional = true }
 zip = { version = "8", default-features = false, features = ["deflate"], optional = true }
 base64 = { version = "0.23", optional = true }
+# Safe TCP keepalive setup for `network://` receive (dead-peer detection);
+# `all` provides TcpKeepalive::with_retries.
+socket2 = { version = "0.6", features = ["all"], optional = true }
+# Safe readiness poll (poll/WSAPoll) so a halt-aware `network://` receive never
+# arms SO_RCVTIMEO, which on Windows can drop data when it cancels a recv.
+rustix = { version = "1", default-features = false, features = ["std", "event"], optional = true }
 # Read-only XML DOM parser (pure Rust, forbid(unsafe_code), entity-expansion
 # bounded). Parses the HD-DVD Advanced-Content playlist `ADV_OBJ/VPLST000.XPL`
 # — untrusted disc bytes — into authoritative titles/clips/chapters. A real