docs(openspec): archive android-auto-favorite-groups

Merges its delta requirements into the android-auto-media base spec.

openspec/specs/android-auto-media/spec.md

@@ -18,10 +18,52 @@ The app MUST declare itself as a media app to Android Auto so the car head unit
 - AND the `AndroidManifest.xml` `<application>` block declares `<meta-data android:name="com.google.android.gms.car.application" android:resource="@xml/automotive_app_desc"/>`
 - AND PluriWave appears in the car's media app list
 
+### Requirement: Favorite Group Sub-Folders
+
+The Android Auto browse tree MUST expose favorite groups (`GrupoFavoritos`, as already modeled by `Emisora.grupoFavoritosId` and surfaced by `EstadoRadio.gruposFavoritos`) as browsable, non-playable sub-folders reachable from the existing `Favoritos` folder, without altering the 3 root folders (`Favoritos`, `Todas las emisoras`, `Mis emisoras`).
+
+#### Scenario: Car requests the Favoritos folder and groups exist
+
+- GIVEN the user has one or more favorite groups with at least one member station each
+- WHEN `getChildren` is called with the `Favoritos` folder id
+- THEN it returns one non-playable folder `MediaItem` per surfaced group, in addition to (or instead of, per the design's structural decision) any ungrouped favorite stations
+- AND each group folder's id follows a browsable `grupo:<id>` scheme distinct from the `emisora:<uuid>` playable-item scheme
+
+#### Scenario: Car requests a group folder's stations
+
+- GIVEN a favorite group folder with id `grupo:<id>` was returned under `Favoritos`
+- WHEN `getChildren` is called with that `grupo:<id>` folder id
+- THEN it returns the playable `MediaItem`s for exactly the stations whose `Emisora.grupoFavoritosId` matches `<id>`
+- AND those items are sorted and capped using the same ordering and item-count rules already applied to the other folders (`ordenarEmisoras`, 50-item cap)
+- AND selecting one of those items plays the corresponding station via the existing `emisora:<uuid>` playback path, unchanged
+
+#### Scenario: Car requests an unknown or stale group id
+
+- GIVEN a `grupo:<id>` id that does not match any group known to the current snapshot
+- WHEN `getChildren` is called with that id
+- THEN it returns an empty list, not an error
+
+### Requirement: Empty Favorite Group Handling
+
+The system MUST produce a browsable tree that never presents a user-selectable folder promising content it cannot deliver: for any favorite group with zero member stations, the tree MUST either omit that group's folder from `Favoritos`'s children, or include it and return an empty (not erroring) child list when browsed. The specific choice between omitting empty-group folders and showing-but-empty, and any related folder-count/flat-vs-nested structural decision for `Favoritos`, is deferred to `sdd-design`; whichever mechanism design selects MUST satisfy both scenarios below.
+
+#### Scenario: Empty group folder is browsed (if shown)
+
+- GIVEN a favorite group has zero member stations and the design's chosen mechanism surfaces it as a folder under `Favoritos`
+- WHEN `getChildren` is called with that group's `grupo:<id>`
+- THEN it returns an empty list, not an error
+
+#### Scenario: No user-facing dead end
+
+- GIVEN the full set of favorite groups, including any empty ones
+- WHEN the `Favoritos` folder is browsed and then each of its returned children is browsed
+- THEN no returned folder child ever throws, hangs, or surfaces a driver-facing error state
+- AND the car head unit's total folder/item count presented under `Favoritos` remains within the driver-distraction-safe bounds design establishes
+
 ### Requirement: Browsable Media Tree
 
-`getChildren` MUST return a browsable tree rooted at `AudioService.browsableRootId`, organized into non-playable folders (Favoritos, Todas las emisoras, Mis emisoras) containing playable station items. Playable station items SHOULD carry an audio-quality subtitle when known.
-(Previously: no subtitle requirement; folders and playable items were otherwise unchanged.)
+`getChildren` MUST return a browsable tree rooted at `AudioService.browsableRootId`, organized into non-playable folders (Favoritos, Todas las emisoras, Mis emisoras) containing playable station items. Playable station items SHOULD carry an audio-quality subtitle when known. The `Favoritos` folder additionally MAY contain non-playable favorite-group sub-folders (see "Favorite Group Sub-Folders"); `Todas las emisoras` and `Mis emisoras` remain flat, unchanged by this capability.
+(Previously: `Favoritos` was a flat folder of playable station items only, with no sub-folder nesting.)
 
 #### Scenario: Car requests the root
 
@@ -54,6 +96,13 @@ The app MUST declare itself as a media app to Android Auto so the car head unit
 - THEN `displaySubtitle` SHALL omit the quality hint gracefully (no subtitle, or a subtitle with no quality fragment)
 - AND the subtitle MUST NOT render literal placeholder text such as "null kbps" or "null · null"
 
+#### Scenario: Ungrouped station appears exactly as before (regression guard)
+
+- GIVEN a station's `Emisora.grupoFavoritosId` equals `GrupoFavoritos.sinAsignarId` (`'sin_asignar'`, the default when no group is assigned)
+- WHEN the `Favoritos`, `Todas las emisoras`, or `Mis emisoras` folders are browsed
+- THEN that station appears as a playable `emisora:<uuid>` item in exactly the same folder(s), position (subject to existing sort rules), title, art, and subtitle as it did before favorite-group folders were introduced
+- AND its presence and shape are unaffected by the existence, emptiness, or content of any favorite group
+
 ### Requirement: Playable Item Metadata
 
 Every playable `MediaItem` (station) MUST include a non-empty `title` and a loadable `artUri`. Stations without a logo MUST fall back to on-brand artwork, and stations whose logo URL cannot actually be loaded MUST degrade to the same on-brand fallback instead of rendering broken or blank art. The fallback MUST be visually consistent with the phone UI's per-station rotation rather than a generic launcher-icon copy.