t66: app names on a device that exposes none

The reported Shield names no app: `pm dump com.netflix.ninja` is ~2241 lines of
dumpsys and grep for `application-label` over the whole capture finds nothing.
The probe shipped `| head -300`, which cut the dump BEFORE the package section,
so "no label" was a truncation artefact; the sweep then named every app after
its own package id, and the apps editor pre-filled the `pkg=pkg` row the user
read as a bug.

  * the probe greps ON THE DEVICE for the three shapes Android prints
    (`application-label`, `nonLocalizedLabel`, `labelRes`); a quoted value is a
    name, `null` and a resource id are not. The dump is never truncated.
  * after APP_LABEL_PROBE_LIMIT consecutive "ran, no label" answers the device
    is taken at its word: the sweep stops spending a shell per package
    (APP_LABEL_TTL expiry re-checks, and a package whose probe FAILED still owes
    its retry — t57 UNIT 0 survives, driven by the app on screen).
  * ONE precedence chain in `ha_adb_common/app_label.resolve_package_name`, used
    by the media player, the Current App sensor, the discovery table, the source
    list and the apps editor: user map > device label > curated map > package id
    (the id shown ONCE, `name` empty when nothing names the app).
  * the curated table covers the user's 21 apps (community-maintained, not
    device truth) and the Configure row says when the device named nothing.
  * the real device shape is a test fixture (trimmed, and marked as such in the
    file: the raw capture is not in the repo) pinning that no label is
    extracted, that the probe count is bounded, and that `Netflix` surfaces.

Also drops the dead `ATTR_MEDIA_DAG_NOW_PLAYING` re-exports left by the t65
flattening and updates the RESEARCH_SHIELD now-playing note to the flat names.

No real Shield was available: the fetch/burst behaviour is exercised against the
documented Android output and the trimmed reproduction of the reported capture.

docs/RESEARCH_SHIELD.md

@@ -404,7 +404,7 @@ covers what the external pieces provided:
 
 | External piece | What it provided | Now native (file) |
 |---|---|---|
-| `mediasession2mqtt` bridge sensors | per-app now-playing pushed over MQTT from the Shield's notification listener | ADB media-session polling + the foreground tier (`connection.py`, `media_player.py`); the `media_dag_now_playing` attribute carries `source: jellyfin \| media_session \| app` |
+| `mediasession2mqtt` bridge sensors | per-app now-playing pushed over MQTT from the Shield's notification listener | ADB media-session polling + the foreground tier (`connection.py`, `media_player.py`); the reading is published as separate top-level `now_playing_*` attributes, and `now_playing_via` names the tier (`jellyfin` \| `media_session` \| `app`) |
 | Universal media player `media_dag_running_apps` template | app switcher list with playback states | `running_apps_from_tasks(..., last_known=...)` (`ha_adb_common/running_apps.py`) — enriched with `foreground`/`state`/`last_known_state`/`last_known_title` |
 | Universal player "currently in app X" template | fallback state for no-session apps | the foreground ladder tier (`media_player.py` state property, tier 3.5) |
 | External androidtv_remote entity for commands | remote keys | the protocol-backed `remote` entity (Phase 2) — the external entity remains only as the transitional last command tier, removed in Phase 4 |