domain: primaryImageTag -> imageId end-to-end (phase 4a/4b)

Rust: PlayerMediaItem and MergedMediaItem gain image_id (dual-carry),
populated from primary_image_tag at every construction/conversion site.
Regenerated bindings.

Frontend: all catalog + player + merged readers now use imageId. The
NowPlayingItem->MediaItem bridge (player.ts) properly maps the remote
session's Jellyfin fields (Type, runTimeTicks, primaryImageTag) onto the
neutral kind/durationMs/imageId. Types that are genuinely out of scope
(Person, NowPlayingItem, PlayItemRequest) keep primaryImageTag.

Rust 456, frontend 644, check clean.

src-tauri/src/commands/player/mod.rs

@@ -106,6 +106,8 @@ pub struct MergedMediaItem {
     pub album_id: Option<String>,
     pub duration: Option<f64>,
     pub primary_image_tag: Option<String>,
+    /// Neutral image identifier — replaces `primary_image_tag` (same value).
+    pub image_id: Option<String>,
     pub media_type: String,
 }
 
@@ -120,6 +122,7 @@ impl From<&crate::player::MediaItem> for MergedMediaItem {
             album_id: item.album_id.clone(),
             duration: item.duration,
             primary_image_tag: item.primary_image_tag.clone(),
+            image_id: item.primary_image_tag.clone(),
             media_type: match item.media_type {
                 crate::player::MediaType::Audio => "audio".to_string(),
                 crate::player::MediaType::Video => "video".to_string(),
@@ -142,6 +145,7 @@ impl From<&crate::jellyfin::client::NowPlayingItem> for MergedMediaItem {
             album_id: item.album_id.clone(),
             duration: item.run_time_ticks.map(|ticks| ticks as f64 / 10_000_000.0),
             primary_image_tag: item.primary_image_tag.clone(),
+            image_id: item.primary_image_tag.clone(),
             media_type: item
                 .item_type
                 .clone()
@@ -361,10 +365,11 @@ pub(super) async fn create_media_item(
         artist_items: None,      // Not available from video-only request
         artists: None,           // Not available from video-only request
         primary_image_tag: None, // Not available from video-only request
-        item_type: None,         // Not available from video-only request
-        playlist_id: None,       // Not available from video-only request
-        duration: None,          // Not available from video-only request
-        artwork_url: None,       // Not available from video-only request
+        image_id: None,
+        item_type: None,   // Not available from video-only request
+        playlist_id: None, // Not available from video-only request
+        duration: None,    // Not available from video-only request
+        artwork_url: None, // Not available from video-only request
         media_type: crate::player::MediaType::Video, // Video-only request
         source,
         video_codec: Some(req.video_codec),
@@ -595,6 +600,7 @@ pub async fn player_enter_background_audio(
         artist_items: None,
         artists: None,
         primary_image_tag: item.primary_image_tag.clone(),
+        image_id: item.primary_image_tag.clone(),
         item_type: None,
         playlist_id: None,
         // Carry the real duration so the lockscreen MediaSession can draw a scrubber.
@@ -1771,6 +1777,7 @@ pub async fn player_play_album_track(
             artist_items: track.artist_items.clone(), // For clickable artist links
             artists: track.artists.clone(),           // Fallback artist info
             primary_image_tag: track.primary_image_tag.clone(), // For frontend image display
+            image_id: track.primary_image_tag.clone(),
             item_type: Some(track.item_type.clone()), // Frontend compatibility
             playlist_id: None,
             duration: track.runtime_ticks.map(|t| t as f64 / 10_000_000.0),
@@ -1966,6 +1973,7 @@ pub async fn player_play_tracks(
             artist_items: track.artist_items.clone(), // For clickable artist links
             artists: track.artists.clone(),           // Fallback artist info
             primary_image_tag: track.primary_image_tag.clone(), // For frontend image display
+            image_id: track.primary_image_tag.clone(),
             item_type: Some(track.item_type.clone()), // Frontend compatibility
             playlist_id: None,                        // Set based on context below
             duration: track.runtime_ticks.map(|t| t as f64 / 10_000_000.0),
@@ -2428,6 +2436,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,

src-tauri/src/commands/player/queue.rs

@@ -211,6 +211,7 @@ pub async fn player_add_track_by_id(
         artist_items: track.artist_items.clone(), // For clickable artist links
         artists: track.artists.clone(),           // Fallback artist info
         primary_image_tag: track.primary_image_tag.clone(), // For frontend image display
+        image_id: track.primary_image_tag.clone(),
         item_type: Some(track.item_type.clone()), // Frontend compatibility
         playlist_id: None,
         duration: track.runtime_ticks.map(|t| t as f64 / 10_000_000.0),
@@ -329,6 +330,7 @@ pub async fn player_add_tracks_by_ids(
             artist_items: track.artist_items.clone(), // For clickable artist links
             artists: track.artists.clone(),           // Fallback artist info
             primary_image_tag: track.primary_image_tag.clone(), // For frontend image display
+            image_id: track.primary_image_tag.clone(),
             item_type: Some(track.item_type.clone()), // Frontend compatibility
             playlist_id: None,
             duration: track.runtime_ticks.map(|t| t as f64 / 10_000_000.0),

src-tauri/src/domain/from_jellyfin.rs

@@ -119,7 +119,10 @@ mod tests {
 
     #[test]
     fn channel_and_container_types_map() {
-        assert_eq!(kind_from_jellyfin("TvChannel", false), MediaKind::LiveChannel);
+        assert_eq!(
+            kind_from_jellyfin("TvChannel", false),
+            MediaKind::LiveChannel
+        );
         assert_eq!(kind_from_jellyfin("Channel", false), MediaKind::Channel);
         assert_eq!(
             kind_from_jellyfin("CollectionFolder", true),

src-tauri/src/playback_mode/mod.rs

@@ -948,6 +948,7 @@ mod tests {
                 artist_items: None,
                 artists: Some(vec!["Test Artist".to_string()]),
                 primary_image_tag: None,
+                image_id: None,
                 item_type: Some("Audio".to_string()),
                 playlist_id: None,
                 duration: Some(180.0),
@@ -979,6 +980,7 @@ mod tests {
                 artist_items: None,
                 artists: Some(vec!["Test Artist".to_string()]),
                 primary_image_tag: None,
+                image_id: None,
                 item_type: Some("Audio".to_string()),
                 playlist_id: None,
                 duration: Some(180.0),

src-tauri/src/player/backend.rs

@@ -380,6 +380,7 @@ mod tests {
             artist_items: None,
             artists: Some(vec!["Test Artist".to_string()]),
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Audio".to_string()),
             playlist_id: None,
             duration: Some(180.0),
@@ -438,6 +439,7 @@ mod tests {
             artist_items: None,
             artists: Some(vec!["Test Artist".to_string()]),
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Audio".to_string()),
             playlist_id: None,
             duration: Some(180.0),
@@ -490,6 +492,7 @@ mod tests {
             artist_items: None,
             artists: Some(vec!["Test Artist".to_string()]),
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Audio".to_string()),
             playlist_id: None,
             duration: Some(180.0),

src-tauri/src/player/media.rs

@@ -67,9 +67,16 @@ pub struct MediaItem {
     /// Artists as array of strings (fallback when artist_items not available)
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub artists: Option<Vec<String>>,
-    /// Primary image tag for artwork
+    /// Primary image tag for artwork.
+    ///
+    /// Legacy Jellyfin name; being replaced by `image_id` (same value). Dual-carried
+    /// while the frontend migrates (docs/specs/frontend-domain-model.md).
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub primary_image_tag: Option<String>,
+    /// Neutral image identifier the frontend resolves to a URL — replaces
+    /// `primary_image_tag`.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub image_id: Option<String>,
     /// Item type (Audio, Movie, Episode, etc.)
     #[serde(rename = "type", default, skip_serializing_if = "Option::is_none")]
     pub item_type: Option<String>,
@@ -345,6 +352,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,
@@ -380,6 +388,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,
@@ -414,6 +423,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,
@@ -448,6 +458,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,
@@ -489,6 +500,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: None,
             playlist_id: None,
             duration: None,
@@ -523,6 +535,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Movie".to_string()),
             playlist_id: None,
             duration: Some(120.0),

src-tauri/src/player/mod.rs

@@ -1397,6 +1397,7 @@ mod tests {
                 artist_items: None,
                 artists: Some(vec!["Test Artist".to_string()]),
                 primary_image_tag: None,
+                image_id: None,
                 item_type: Some("Audio".to_string()),
                 playlist_id: None,
                 duration: Some(180.0),

src-tauri/src/player/queue.rs

@@ -551,6 +551,7 @@ mod tests {
                 artist_items: None,
                 artists: Some(vec!["Artist".to_string()]),
                 primary_image_tag: None,
+                image_id: None,
                 item_type: Some("Audio".to_string()),
                 playlist_id: None,
                 duration: Some(180.0),

src-tauri/src/player/session.rs

@@ -242,6 +242,7 @@ mod tests {
             artist_items: None,
             artists: Some(vec!["Test Artist".to_string()]),
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Audio".to_string()),
             playlist_id: None,
             duration: Some(180.0),
@@ -272,6 +273,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Movie".to_string()),
             playlist_id: None,
             duration: Some(7200.0),

src-tauri/src/player/state.rs

@@ -323,6 +323,7 @@ mod tests {
             artist_items: None,
             artists: None,
             primary_image_tag: None,
+            image_id: None,
             item_type: Some("Video".to_string()),
             playlist_id: None,
             duration: Some(100.0),

src-tauri/src/repository/offline.rs

@@ -128,8 +128,7 @@ impl OfflineRepository {
                 let playback_position_ticks: Option<i64> = row.get(0).ok();
                 Ok(UserData {
                     playback_position_ticks,
-                    playback_position_ms: playback_position_ticks
-                        .map(crate::domain::ticks_to_ms),
+                    playback_position_ms: playback_position_ticks.map(crate::domain::ticks_to_ms),
                     is_played: row.get::<_, Option<i32>>(1).ok().flatten().map(|v| v != 0),
                     is_favorite: row.get::<_, Option<i32>>(2).ok().flatten().map(|v| v != 0),
                     play_count: row.get(3).ok(),