fix(remote-hls): give the bypass a terminal state and act on a settled carriage verdict (#334)

[superuser404notfound]

Re #334. Found while verifying #321 against a synthetic live master.

A nativeRemoteHLS session whose item never reaches readyToPlay had no way out. The lean bypass runs without a readiness watchdog on purpose and leaves a dead upstream to AVPlayer's own "gave up" signal, which covers an origin that stops answering. It does not cover one that answers everything while AVFoundation builds no track from what it serves: nothing fails, nothing becomes ready, state stays .loading.

The carriage machinery could not rescue it, because all of it hangs off the same anchor: the #293 probe settled hevcInMPEGTS and the verdict was then only read by a loop that arms at readyToPlay, and the deferred segment-head probe waited out its 20 s readiness ceiling and returned without reading the one thing that could judge the source.

Three changes

1. A settled verdict reroutes on its own. It is read off the source's playlists or PMT and needs no grace. A video track that does exist still outranks it, so a source contradicting the probe keeps its native session.
2. The deferred probe reads the segment head when the ceiling expires instead of abandoning the case. Deferring existed so the read would not compete with the mount; a mount that has not settled in 20 s is not competing for anything.
3. The bypass gets a ceiling on silence. 45 s with no readiness, no reroute and no failure publishes a real error. Readiness at any point, a reroute, or an AVPlayer failure disarm it, so a slow IPTV handshake or a Jellyfin transcode spin-up never meets it. The budget also clears the deferred probe's own 20 s ceiling plus its segment read, which is asserted in a test rather than left to a comment.

Verification

12 new tests (verdict-acts-without-readiness table, deadline table), 1618 tests in 240 suites green, -strict-concurrency=complete clean, tvOS Simulator BUILD SUCCEEDED.

Each layer was also run against a synthetic live master carrying HEVC in MPEG-TS with no audio track, which is the shape that produced the hang:

Fixture	Before	After
CODECS="hvc1..."	25 s in state=loading, verdict logged and unused	reroutes ~1 s in, state=playing
no CODECS	same hang, segment head never read	ceiling log, head read, reroute at ~20 s, plays
CODECS="avc1..." while carrying HEVC	hang with nothing able to judge it	terminal .error at 45 s

Internal surface only (RemoteHLSReadinessDeadline and the new load(readinessDeadline:) parameter are not public), so this is a patch-level behaviour fix: sessions that used to hang now either play or fail.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HX5zV3Fcf7Nzq4DYGdXvQE