Emulator helper so tests start in seconds, not minutes

The Google TV emulator was launched by hand with -no-snapshot, which forces
a cold boot every time. tests/helpers/emulator.sh boots from the AVD's
default_boot snapshot (~7s) and refreshes that snapshot on stop, so the next
run stays fast. It also wraps the two things a test run needs afterwards:
installing an APK and pulling a screenshot into tests/runs/.

CONTEXT.md's example dialogue still described Xtream credentials entered
through the Remote, which ADR-0005 and ADR-0007 replaced with device flow and
phone-side onboarding.

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

CONTEXT.md

@@ -73,9 +73,10 @@ Channel, no full guide timeline.
 ## Example dialogue
 
 > **Dev:** "Does the **Remote** need Backend credentials?"
-> **Domain expert:** "No — the user enters the Xtream credentials of a
-> **Quelle** once via the Remote, the **TV-App** stores them and is the only
-> one talking to the **Backend**."
+> **Domain expert:** "No — the Remote is where **Onboarding** happens, not
+> where credentials live: the user types the server URL there and finishes the
+> IdP login on the phone. The **TV-App** holds the tokens and is the only one
+> talking to the **Backend**. A generic M3U **Quelle** needs no login at all."
 
 ## Flagged ambiguities
 

README.md

@@ -79,4 +79,22 @@ sind signiert; über einem Debug-Build muss einmal deinstalliert werden
 (Signaturwechsel). Updates bezieht die App über die Release-API dieses
 Repos, die APK selbst liegt auf dem Branch `apk`.
 
+### Tests
+
+```
+./gradlew test                         # Unit-Tests, Reports unter tests/runs/
+tests/helpers/emulator.sh start        # headloser Google-TV-Emulator
+tests/helpers/emulator.sh install app/build/outputs/apk/debug/app-debug.apk
+tests/helpers/emulator.sh shot name    # Screenshot nach tests/runs/screenshots/
+tests/helpers/emulator.sh stop
+```
+
+Der Emulator (AVD `castarr-googletv`, API 34) startet aus einem Snapshot und
+ist in wenigen Sekunden oben; `stop` schreibt den Snapshot vorher neu. Ein
+Kaltstart entsteht nur, wenn der Snapshot fehlt.
+
+Demo-Daten für einen Lauf ohne echtes Backend: `tests/demo/make-demo-data.py`
+erzeugt Playlist und EPG, die ein lokaler HTTP-Server als generische Quelle
+ausliefert.
+
 Architektur-Notizen: [CONTEXT.md](CONTEXT.md) und [docs/adr/](docs/adr/).

tests/helpers/emulator.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# Headless Google-TV emulator for test runs.
+#
+# The AVD keeps a "default_boot" snapshot, so a start restores a booted
+# system in seconds instead of cold-booting for minutes. "stop" refreshes
+# that snapshot before killing, so the next start stays fast.
+#
+#   tests/helpers/emulator.sh start        # boot (or restore) and wait
+#   tests/helpers/emulator.sh stop         # snapshot, then kill
+#   tests/helpers/emulator.sh status
+#   tests/helpers/emulator.sh install <apk>
+#   tests/helpers/emulator.sh shot <name>  # screenshot into tests/runs/screenshots
+set -euo pipefail
+
+AVD="${CASTARR_AVD:-castarr-googletv}"
+SERIAL="${CASTARR_SERIAL:-emulator-5554}"
+SDK="${ANDROID_SDK_ROOT:-$HOME/Android/Sdk}"
+ADB="$SDK/platform-tools/adb"
+EMULATOR="$SDK/emulator/emulator"
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+RUNS="$ROOT/tests/runs"
+LOG="$RUNS/emulator.log"
+
+booted() { [ "$("$ADB" -s "$SERIAL" shell getprop sys.boot_completed 2>/dev/null | tr -d '\r')" = "1" ]; }
+
+start() {
+  if booted; then echo "already up: $SERIAL"; return 0; fi
+  mkdir -p "$RUNS"
+  # No -no-snapshot here: that is what makes a start slow.
+  nohup "$EMULATOR" -avd "$AVD" \
+    -no-window -no-audio -no-boot-anim \
+    -gpu swiftshader_indirect \
+    >"$LOG" 2>&1 &
+  local start_ts=$SECONDS
+  "$ADB" -s "$SERIAL" wait-for-device
+  for _ in $(seq 1 180); do
+    booted && { echo "up after $((SECONDS - start_ts))s"; return 0; }
+    sleep 1
+  done
+  echo "timeout waiting for boot; see $LOG" >&2
+  return 1
+}
+
+stop() {
+  if ! pgrep -f "qemu-system-.*-avd $AVD" >/dev/null 2>&1 && ! booted; then
+    echo "not running"; return 0
+  fi
+  # Refresh the snapshot so the next start is a restore, not a cold boot.
+  "$ADB" -s "$SERIAL" emu avd snapshot save default_boot
+  "$ADB" -s "$SERIAL" emu kill
+  echo "stopped, snapshot saved"
+}
+
+case "${1:-status}" in
+  start)  start ;;
+  stop)   stop ;;
+  status) booted && echo "up: $SERIAL" || echo "down" ;;
+  install)
+    [ $# -ge 2 ] || { echo "usage: $0 install <apk>" >&2; exit 2; }
+    "$ADB" -s "$SERIAL" install -r "$2"
+    ;;
+  shot)
+    name="${2:-shot}"
+    mkdir -p "$RUNS/screenshots"
+    "$ADB" -s "$SERIAL" exec-out screencap -p > "$RUNS/screenshots/$name.png"
+    echo "$RUNS/screenshots/$name.png"
+    ;;
+  *) echo "usage: $0 {start|stop|status|install <apk>|shot <name>}" >&2; exit 2 ;;
+esac