feat(dev): an Android failure looks exactly like a success

The APK installs and launches. It also dies six milliseconds later, and
finding that out cost a cycle for three reasons that have nothing to do
with the bug itself:

**Go's stdout does not reach logcat.** An Android app's fd 1 and 2 go
to /dev/null, so every slog line -- including the one naming the error
the app is about to exit on -- is discarded. `setprop
log.redirect-stdio true` does not help: that redirects the Java
runtime's System.out, and our code is a c-shared native library.

**os.Exit leaves no evidence.** No panic, no AndroidRuntime stack,
nothing in /data/tombstones, nothing in `logcat -b crash` or dropbox.
All three places anyone would look are empty, and the one signal that
is present -- "Zygote: exited due to signal 9" -- reads as "the system
killed it" and sends you after the low-memory killer.

**ActivityManager restarts it faster than you can observe.** pidof
always answers and `am start` always reports Status: ok, so a
crash-looping app looks alive. "Did it start" is the wrong question;
`make android-smoke` asks whether it is the *same pid* N seconds later,
and prints the filtered logcat plus how to read it when it is not.

The tell, once known: "I/WailsBridge: Wails bridge initialized"
followed immediately by a new pid doing the same thing.

scripts/android-emulator.sh follows dev-headless.sh's shape --
background start, saved-PID stop, filtered log tail, never pkill -f.
Two scaffold tasks are deliberately not wrapped: `android:logs` greps
logcat for (Wails|yellowjacket), which catches the WailsBridge tag but
misses the app's own process tag (app.yellowjacket is lowercase) and
misses ActivityManager's "has died" line, which is the one that says it
crashed; and `ensure-emulator` boots whatever `-list-avds | tail -1`
returns, with no pidfile and no boot wait, so it cannot be sequenced.

One environment note that is not obvious on Arch: Gradle needs a
platform and /opt/android-sdk has none, so ANDROID_SDK defaults to
~/Android/Sdk while ANDROID_NDK points at /opt/android-ndk. Two SDKs,
one for each half of the build.

.pi/skills/yellowjacket-dev/SKILL.md

@@ -151,6 +151,7 @@ only climb when it cannot.
 | Something you cannot predict — exploring | `make dev-headless SEED=default` + `playwright-cli` | interactive |
 | Something whose answer is a *number*, not a pass | `make perf` against a bulk-seeded app | ~1 min + setup |
 | A `.sql` or `.templ` file | `make generate`, then the checklist in [references/schema-change.md](references/schema-change.md) | |
+| Anything that has to survive on a phone | `make android-smoke` against a booted emulator | ~1 min + setup |
 
 Two targets are once-per-clone prerequisites that are **not**
 dependencies of the targets needing them, so on a fresh checkout each
@@ -426,3 +427,9 @@ fails the build otherwise, including in files no lint pass compiles.
   and what breaks in it.
 - [schema-change.md](references/schema-change.md) — the two-file
   schema/migration checklist.
+- [android-tier.md](references/android-tier.md) — the emulator tier,
+  and the three reasons a failure there looks like a success. **Read
+  its first section before running anything on Android**: Go's stdout
+  does not reach logcat, `os.Exit` leaves no panic and no tombstone,
+  and ActivityManager restarts a dying app fast enough that `pidof`
+  always answers.