scripts: bridge-emulator.sh (host) + image prefetching

Perf work for the TV FPS complaint: every page that loads from the API
also warms Coil's disk/memory caches (video thumbnails at the same
480x270 the card renders, channel banners/avatars) so rows scroll
without popping in over the network. Prefetch keys match render keys
exactly so cache hits are guaranteed.

bridge-emulator.sh runs OUTSIDE the container on the emulator host:
boots jtubesc if needed (ADB_VENDOR_KEYS whitelists the host adb key),
installs/starts JTube TV and binds :5557 -> adbd 5601 so the container
and LAN can drive it. Run it once in your rutherford shell.

scripts/bridge-emulator.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+#
+# bridge-emulator.sh — (host-side) expose the emulator's adbd to the LAN so agents
+# inside the container/other machines can use it: binds :5557 -> 127.0.0.1:5601.
+# The emulator console transport (emulator-5600) stays local-only; this bridges the
+# adbd TCP port 5601.
+set -euo pipefail
+ADBD_PORT=5601
+BRIDGE_PORT=5557
+
+# start emulator if not running
+ADB="${ANDROID_SDK_ROOT:-$HOME/Android/Sdk}/platform-tools/adb"
+if ! "$ADB" devices | grep -q "emulator-5600.*device"; then
+  echo "emulator-5600 not running — starting it…"
+  ADB_VENDOR_KEYS="$HOME/.android/adbkey" setsid nohup \
+    "${ANDROID_SDK_ROOT:-$HOME/Android/Sdk}/emulator/emulator" -avd jtubesc -port 5600 \
+    -no-window -gpu swiftshader_indirect -no-snapshot -no-audio -no-boot-anim \
+    > /tmp/jtube-emu.log 2>&1 < /dev/null &
+  echo "waiting for boot (log: /tmp/jtube-emu.log)…"
+  for i in $(seq 1 60); do
+    ok=$("$ADB" -s emulator-5600 shell getprop sys.boot_completed 2>/dev/null | tr -d '\r')
+    [ "$ok" = "1" ] && { echo "BOOTED"; break; }
+    sleep 5
+  done
+fi
+
+# keep JTube TV installed + running
+APK="$HOME/Projects/jtube-tv/app/build/outputs/apk/debug/app-debug.apk"
+if [ -f "$APK" ]; then
+  "$ADB" -s emulator-5600 install -r "$APK" >/dev/null && echo "JTube TV installed"
+  "$ADB" -s emulator-5600 shell am start -n net.jeena.jtubetv/.MainActivity && echo "app started"
+fi
+
+# the bridge (bind all LAN addresses)
+if ! ss -tln 2>/dev/null | grep -q ":$BRIDGE_PORT"; then
+  setsid nohup socat TCP-LISTEN:$BRIDGE_PORT,bind=0.0.0.0,fork,reuseaddr \
+    TCP:127.0.0.1:$ADBD_PORT > /tmp/jtube-bridge.log 2>&1 < /dev/null &
+  echo "bridge: :$BRIDGE_PORT -> 127.0.0.1:$ADBD_PORT (pid $!)"
+fi
+
+echo "From this host:      adb connect localhost:$BRIDGE_PORT"
+echo "From other machines: adb connect rutherford:$BRIDGE_PORT"