A module declares SourceDriverInterface classes in module.json
("source_drivers", optional "start_timeout") and claims URL schemes of its
own; core runs the driver's engine in ffmpeg's place for those sources.
- SourceDriverRegistry: scheme -> driver, loaded via ModuleLoader::loadAll()
(no bootAll, so the streaming entry point works), core schemes reserved,
a scheme claimed by two modules goes to neither, unknown schemes refused.
- StreamProcess: per-source choice in the supervised spec and the PHP
monitor path; ffmpeg-only settings (transcode, maps, RTMP, delay…) refuse
the driver; argv escaped by core, must name the playlist; no fallback_cmd
or probe_cmd; the driver's start_timeout extends the start wait.
- ProcessManager recognises a driver engine by binary + playlist, so
monitor, stop and cron treat it as the stream's producer.
- MonitorCommand priority/force checks go through sourceAnswers()
(driver's available() or ffprobe).
- Offset the added branches in startStream/buildSupervisorSpec/producerKind
with behaviour-preserving simplifications (CRAP ratchet).
