Split the API 37 leg so the part that works can gate

CI has never run the API level this app targets. The reason it did not was
never "API 37 is untestable" -- it was that two tests fail on the emulator
image, so one row would be permanently red or permanently allow-listed. This
splits that row instead of choosing between those two.

E2E API 37 gates. It runs 55 of the suite's 57 instrumented tests and must be
green. E2E API 37 Media3 hardware transcode runs the other two, reports, and
never blocks (continue-on-error). Both are driven off ONE marker,
@FailsOnEmulatorApi37: the gating job passes notAnnotation, the advisory job
passes annotation. Two lists would drift, and drift is silent in both
directions -- a test that ends up in neither job reads as green. Excluding by
class was not an option either: Media3EngineTest has four tests and two of
them pass here, so notClass would have thrown away real coverage.

The advisory job is named for what it runs, not for what we think is wrong.
Both its tests drive a full H.264 -> H.265 hardware transcode, which is what
distinguishes them from the two Media3EngineTest cases that pass -- those
never decode video. The goldfish-decoder theory sits in a comment inside the
job, where it can be corrected without renaming a check people have learned to
look for; docs/api-37-emulator-crash.md keeps measurement and inference apart.

The SystemUI disable moves into .github/scripts/e2e-run.sh behind
E2E_DISABLE_SYSTEM_UI, unset everywhere but the two API 37 jobs, so the other
four legs run byte-identical commands -- the same shape as
E2E_EXTRA_GRADLE_ARGS. It runs BEFORE the streamed logcat starts, deliberately:
`adb shell stop` would end that logcat and nothing restarts it, so a disable
placed after it would cost the leg its diagnostics for the part of the run that
matters. The body is probe v2 from api37-debug.yml -- the version measured 4/4
-- not the older one-round form: three rounds, waits for system_server to
actually be gone, verifies against `pm list packages -d`, and requires a 45 s
window with zero new aborts. The weaker probe reported success on a run that
then started SystemUI eight more times.

The caveat is written next to the row rather than left implicit: this leg runs
with SystemUI disabled and the framework restarted under it, a device
configuration no other leg and no Pixel run uses. Anything that touches system
UI must not trust it, and the Pixel check before each release is still the only
API 37 run with SystemUI intact.

docs/api-37-emulator-crash.md's "So should CI take API 37?" said no on three
reasons. Two were claims about CI that had never been measured; the section now
carries the eight runs that measured them, and the third reason is what the
split answers. docs/local-emulator.md and api37-debug.yml's header carried the
same "the matrix stops at 36" claim and are corrected with it.

CLAUDE.md is left alone deliberately -- its "CI's matrix therefore stops at API
36" clause is now false, and that correction is parked in the doc's existing
"Correction owed to CLAUDE.md" section, where two others are already waiting.

Making E2E API 37 an actually-required check is a repository-settings change
and must come after this is on main: adding a required context that does not
exist on the default branch blocks every PR.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/androidTest/java/org/libremediaconverter/FailsOnEmulatorApi37.kt

@@ -0,0 +1,24 @@
+package org.libremediaconverter
+
+/**
+ * Marks an instrumented test that does not pass on the `android-37.x` **emulator** system images.
+ *
+ * This is a marker, not a skip. Nothing reads it except CI, and CI reads it twice — once with
+ * `notAnnotation` to build the gating API 37 leg, and once with `annotation` to build the advisory
+ * one — so a test carrying it runs in exactly one of the two and can never fall through both.
+ * That is the whole reason there is one annotation rather than a pair of test lists: two lists
+ * drift, and the drift is silent in both directions (a test that runs nowhere reads as green).
+ *
+ * It says only what has been measured: **on the emulator, at API 37.** The same tests pass on a
+ * physical Pixel 10 Pro XL at API 37 and at API 33–36 on the same runner under the same renderer,
+ * so this must never be read as "this test is allowed to fail at API 37" — only as "the API 37
+ * emulator image cannot currently answer this one". `docs/api-37-emulator-crash.md` has the
+ * measurements and the one bullet in them that is still inference.
+ *
+ * Removing it is the goal, and the trigger is written down: a new API 37.x system image, or an
+ * ATD image for 37. Delete the annotation from the tests, and the advisory job goes empty and
+ * the gating one grows by two.
+ */
+@Retention(AnnotationRetention.RUNTIME)
+@Target(AnnotationTarget.CLASS, AnnotationTarget.FUNCTION)
+annotation class FailsOnEmulatorApi37

app/src/androidTest/java/org/libremediaconverter/convert/Media3EngineTest.kt

@@ -16,6 +16,7 @@ import org.junit.Assert.assertTrue
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
+import org.libremediaconverter.FailsOnEmulatorApi37
 import org.libremediaconverter.model.ConversionRequest
 import org.libremediaconverter.model.OutputFormat
 import java.io.File
@@ -57,6 +58,7 @@ class Media3EngineTest {
     }
 
     @Test
+    @FailsOnEmulatorApi37
     fun transcodesH264ToH265AndReportsProgress(): Unit = runBlocking {
         val seen = mutableListOf<Int>()
 
@@ -119,6 +121,7 @@ class Media3EngineTest {
      * HandlerThread indirection holds before any of that lands in Phase 2.
      */
     @Test
+    @FailsOnEmulatorApi37
     fun runsFromAThreadWithNoLooper() {
         val pool = Executors.newSingleThreadExecutor()
         try {