fix(streams): the live type key is live, and the schema defaults are not refusals

Two reasons the native remuxer never ran on a real panel, both in the
eligibility check:

- it compared `type_key` against `live_streams`, which is no type at all —
  `streams_types` holds (1, 'Live Streams', 'live'), (3, 'created_live'),
  (4, 'radio_streams'). Every ordinary live channel was refused, so
  `fanout_source_backend` native/auto silently kept running ffmpeg. The new
  log line said it out loud ("ffmpeg runs this stream: not a live channel"),
  which is how it surfaced; the refusal now names the type it saw.
- `gen_timestamps` and `read_native` were treated as "the operator asked for
  timestamp repair / realtime pacing", but both DEFAULT to 1 in `streams`, so
  they carry no intent and refusing them refuses everything. -re paces a
  file-ish input, which a passthrough of a live source does by itself, and
  genpts only synthesises timestamps a source failed to send — a source that
  broken has no usable video clock either, which ends the run with exit 3 and,
  in `auto`, hands it to ffmpeg.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K48c64npichw9ZCZDU16ja

tests/Unit/StreamProcessBuildLiveTest.php

@@ -37,7 +37,7 @@ final class StreamProcessBuildLiveTest extends TestCase {
 					'custom_ffmpeg' => '',
 					'stream_all' => 0,
 					'custom_map' => '',
-					'type_key' => 'live_streams',
+					'type_key' => 'live',
 					'gen_timestamps' => 0,
 					'read_native' => 0,
 					'enable_transcode' => 0,