feat(const,strings,readme): adb_command consts/service name, options toggle strings, curated DEFAULT_APP_DIRECTORY and README service notes (completes P4-2 unit 1)

custom_components/nvidia_shield/const.py

@@ -96,6 +96,20 @@ ZEROCONF_SERVICE_TYPE = "_androidtvremote2._tcp.local."
 # consumed by app_name after the androidtv-entity and protocol-push tiers.
 CONF_APP_NAME_MAP = "app_name_map"
 
+# P4-2a adb_command service: rawADB shell on this entry — OFF by default
+# (same security posture as the core androidtv integration).
+CONF_ADB_COMMAND_ENABLED = "adb_command_enabled"
+SERVICE_ADB_COMMAND = "adb_command"
+
+# P4-2c BrowseMedia app directory fallback when the options map is empty
+# (curated; the packages are the plan's reference apps).
+DEFAULT_APP_DIRECTORY = {
+    "ar.tvplayer.tv": "TiviMate",
+    "com.github.damontecres.wholphin": "Wholphin",
+    "com.netflix.ninja": "Netflix",
+    "com.google.android.youtube.tv": "YouTube",
+}
+
 CHANNEL_DIGIT_DELAY = 0.1
 CONF_CHANNEL_DIGIT_DELAY = "channel_digit_delay"
 CONF_CHANNEL_SEND_ENTER = "channel_send_enter"