Say that Gradle had the same hole the adb wrapper closed

Gradle's install and connected-test tasks never went through that wrapper,
so they reached every attached emulator. emulator-tools now guards them with
a Gradle init script; this records what that means here, and how to name a
device without exporting a serial that goes stale.

Also stop naming one checkout's AVD in a file that is the same in every
clone -- it read as a suggestion to target ai-app-2 from ai-app.

AGENTS.md

@@ -258,11 +258,12 @@ first if a remote spawn ever mangles an argument.
   `adb -s "$SERIAL" shell "am start -a android.intent.action.VIEW -d 'aiapp://enroll?host=10.0.2.2&port=8443&token=…'"`
   (quote so the device shell doesn't eat the `&`s).
 - **The emulator is `~/repos/emulator-tools`' business, not this repo's.**
-  `emu up` creates and boots the AVD named after this checkout (`ai-app-2`),
-  refusing when the machine has no room for one; `emu list` says what is
-  attached and what it costs; `emu down` stops it. `run-android.sh` is that
-  plus a build and an install. Run that repo's `install.sh` once if `emu` is
-  missing.
+  `emu up` creates and boots the AVD named after this checkout — whatever
+  `emu name` prints, never a name typed out here, since this file is the same
+  in every clone — refusing when the machine has no room for one; `emu list`
+  says what is attached and what it costs; `emu down` stops it.
+  `run-android.sh` is that plus a build and an install. Run that repo's
+  `install.sh` once if `emu` is missing.
   The `adb` on `PATH` after sourcing `android-env.sh` is that repo's wrapper,
   which fills in `-s` from the same rule — so a bare `adb shell` reaches this
   checkout's emulator and refuses to reach another one's. That defaulting is
@@ -270,6 +271,16 @@ first if a remote spawn ever mangles an argument.
   and no `-s`, a bare `adb shell pm list packages` comes back **empty**,
   which reads as the app having been uninstalled rather than as the question
   being ambiguous.
+  **Gradle does not go through that wrapper**, so it had the same hole until
+  2026-08-31: `installDebug`, `uninstallDebug` and `connectedAndroidTest` ask
+  the adb server for every attached device and act on all of them, which is
+  how one session's debug build landed on another's emulator. A Gradle init
+  script from `emulator-tools` now runs `emu check` before those tasks and
+  fails the build rather than fanning out. When it refuses, say which device
+  you mean at the moment you use it — `ANDROID_SERIAL=$(emu serial)
+  ./gradlew …` — rather than exporting a serial into the shell, which goes
+  stale the next time an emulator restarts and another checkout's takes the
+  port.
 
 ## Where things run (host vs this VM)