fix(auto): fall back to brand art and surface quality on dead/missing favicons

Android Auto no longer copies the launcher icon as placeholder art; it
rotates through the same 4 on-brand station_art assets the phone UI
already uses, keyed by the same per-station hash for visual parity.
Malformed or unusable favicon URLs (including a Dart Uri quirk where
'http://' reports hasAuthority=true with an empty host) now fail the
validity gate instead of being handed to the OS media browser as-is.
Browsable items also show codec/bitrate as a subtitle when known.

lib/servicios/navegacion_auto.dart

@@ -9,15 +9,75 @@ import '../modelos/emisora.dart';
 import 'persistencia_tolerante.dart';
 import 'servicio_favoritos.dart';
 
-/// URI of the bundled default station artwork, served from
-/// `android/app/src/main/res/drawable` via `android.resource://` (Design
-/// "default artwork delivery" — no per-URI grant needed, works offline, and
-/// cannot 404 unlike a FileProvider content URI or a remote placeholder).
-const String _defaultArtUri =
-    'android.resource://es.freetimelab.pluriwave/drawable/default_station_art';
-
 const _prefijoEmisora = 'emisora:';
 
+/// Canonical on-brand fallback-art names and rotation order, ported
+/// **verbatim** (same formula, same order) from
+/// `lib/widgets/tarjeta_emisora.dart`'s `_fallbackArtFor` (lines 363-367)
+/// to guarantee phone/car per-station art parity (Design "Fallback-art
+/// selection"). Keep this list in sync with that one — there is no
+/// structural enforcement of order, only this comment and the parity test
+/// in `navegacion_auto_test.dart` (group `parity: phone/auto art order`).
+const _nombresArte = ['aurora', 'cosmic', 'pulse', 'nova'];
+
+/// Returns whether [favicon] is usable as a remote `artUri` (Design
+/// Decision "Case B detection" — static validity gate, zero network):
+/// non-null, non-blank after trimming, and parses as an absolute
+/// `http`/`https` URI with a non-empty authority. Does **not** probe
+/// reachability — the OS art loader fetches `artUri` independently and
+/// later, so a build-time network check would be racy (TOCTOU); this only
+/// catches the deterministic malformed/non-http(s) subset (bare hosts,
+/// wrong scheme, `http://` with no authority, whitespace, unparseable).
+bool faviconUsable(String? favicon) {
+  final trimmed = favicon?.trim();
+  if (trimmed == null || trimmed.isEmpty) return false;
+  final uri = Uri.tryParse(trimmed);
+  if (uri == null) return false;
+  // `Uri.hasAuthority` is true whenever a `//` authority slot is present,
+  // even with an empty host (e.g. `Uri.parse('http://').hasAuthority` is
+  // `true`) — check `host.isNotEmpty` explicitly to actually require a
+  // non-empty authority host.
+  return (uri.scheme == 'http' || uri.scheme == 'https') &&
+      uri.host.isNotEmpty;
+}
+
+/// Deterministic rotation index over the 4 on-brand fallback arts, same
+/// formula as `tarjeta_emisora.dart`'s `_fallbackArtFor` (Design
+/// "Fallback-art selection — port verbatim"): `seed` is the station uuid.
+int indiceArtePara(String seed) =>
+    seed.codeUnits.fold<int>(0, (a, b) => a + b) % _nombresArte.length;
+
+/// Resolves the `artUri` for [e] (Design "Data Flow"): the favicon when it
+/// passes [faviconUsable], otherwise a rotating `station_art_<name>`
+/// drawable URI selected via [indiceArtePara] over `e.uuid` — the same
+/// on-brand art the phone UI would pick for this station (per-station
+/// parity), never a launcher-icon lookalike.
+String artUriPara(Emisora e) => faviconUsable(e.favicon)
+    ? e.favicon!
+    : 'android.resource://es.freetimelab.pluriwave/drawable/'
+        'station_art_${_nombresArte[indiceArtePara(e.uuid)]}';
+
+/// Formats a human-readable audio-quality hint for the browse row's
+/// `displaySubtitle` (Design Decision "`displaySubtitle` quality format"):
+/// `"<bitrate> kbps · <CODEC>"` when both are known, just the bitrate or
+/// just the codec when only one is known, and `null` (never `""`, never a
+/// string containing the literal `"null"`) when both are unknown. Codec is
+/// trimmed and upper-cased; blank-after-trim counts as unknown. `bitrate`
+/// `<= 0` counts as unknown (Radio Browser stores `0` for unknown).
+String? subtituloCalidad(Emisora e) {
+  final codec = e.codec?.trim();
+  final codecConocido = codec != null && codec.isNotEmpty;
+  final bitrate = e.bitrate;
+  final bitrateConocido = bitrate != null && bitrate > 0;
+
+  if (codecConocido && bitrateConocido) {
+    return '$bitrate kbps · ${codec.toUpperCase()}';
+  }
+  if (bitrateConocido) return '$bitrate kbps';
+  if (codecConocido) return codec.toUpperCase();
+  return null;
+}
+
 /// Browse-source abstraction for the Android Auto media tree (Design
 /// "getChildren data source, cold-start safe"). Kept separate from
 /// `EstadoRadio` so a headless Auto bind (`main()` runs but the widget tree
@@ -97,21 +157,19 @@ class ConstructorArbolAuto {
   }
 
   /// Maps a single [Emisora] to a playable `MediaItem`: id `emisora:<uuid>`
-  /// (Design "media-id scheme"), title, and artUri with the default-art
-  /// fallback (Design "default artwork delivery").
+  /// (Design "media-id scheme"), title, on-brand-fallback-aware `artUri`
+  /// (Design "Case B detection" + "Fallback-art selection") and a
+  /// quality-hint `displaySubtitle` (Design "`displaySubtitle` quality
+  /// format") when codec/bitrate are known.
   MediaItem itemEmisora(Emisora e) => MediaItem(
     id: '$_prefijoEmisora${e.uuid}',
     title: e.nombre,
     playable: true,
-    artUri: Uri.parse(_artUriPara(e)),
+    artUri: Uri.parse(artUriPara(e)),
+    displaySubtitle: subtituloCalidad(e),
     extras: _contentStyleGrid,
   );
 
-  String _artUriPara(Emisora e) {
-    final favicon = e.favicon;
-    return (favicon != null && favicon.isNotEmpty) ? favicon : _defaultArtUri;
-  }
-
   /// Resolves `emisora:<uuid>` ids to the matching [Emisora] in [universo].
   /// Any other shape (no prefix, empty uuid, unmatched uuid) returns `null`
   /// instead of throwing (Spec "Media Item Resolution by ID").