fix(android): subtitles on the picture, not on a black bar

Every subtitle line arrived in an opaque black box wide enough to sit across
the picture. That box is what Android hands back when the viewer has set no
captioning preferences: SubtitleView.setUserDefaultStyle() reads the system
style and falls back to media3's DEFAULT, which is white on opaque black.

Dropping the box is not the same as replacing the style. Someone who has
configured captions in accessibility settings has said something specific about
colour, typeface and edges, and overriding all of it to remove a background
would answer a question they did not ask. Their style is kept and only the two
colours that paint a box — background and window — are cleared.

A style specifying no edge gets a black outline, since without a box the text
must supply its own contrast or it is unreadable over a bright scene. One that
already names an edge keeps it: that viewer has said how they want their
captions separated from the picture.

Compiles and packages, but NOT yet seen on a device — the tablet was
disconnected before it could be deployed, so the requirement is recorded as
"Done (pending device verification)" and this must not be tagged into a release
until someone has looked at it.

TRACES: UR-020 | DR-261

src-tauri/android/src/main/java/com/dtourolle/jellytau/player/JellyTauPlayer.kt

@@ -1330,10 +1330,8 @@ class JellyTauPlayer(private val appContext: Context) {
                     ViewGroup.LayoutParams.MATCH_PARENT,
                     ViewGroup.LayoutParams.MATCH_PARENT
                 )
-                // Honour the viewer's system captioning preferences (size,
-                // colour, edge style) and whatever styling the track carries —
-                // the same defaults a PlayerView would have applied.
-                setUserDefaultStyle()
+                // Text over the picture, not a black bar across it. (DR-261)
+                setStyle(captionStyle())
                 setUserDefaultTextSize()
             }
             android.util.Log.d("JellyTauPlayer", "SubtitleView created")
@@ -1341,6 +1339,61 @@ class JellyTauPlayer(private val appContext: Context) {
         return videoView!!.hashCode()
     }
 
+    /**
+     * The caption style to draw cues in: the viewer's own, with the background
+     * taken out.
+     *
+     * `setUserDefaultStyle()` reads Android's captioning preferences and falls
+     * back to media3's `DEFAULT` when the viewer has set none — and that
+     * default is white on **opaque black**, which is what put a black box under
+     * every line, wide enough to sit across the picture.
+     *
+     * Dropping the box is not the same as replacing the style. A viewer who has
+     * configured captions in accessibility settings has said something specific
+     * about colour, typeface and edges, and overriding all of that to get a
+     * transparent background would be answering a question they did not ask. So
+     * their style is kept and only the two colours that paint a box —
+     * background and window — are cleared.
+     *
+     * With no box the text supplies its own contrast or it is unreadable over a
+     * bright scene, so a style that asked for no edge gets a black outline. One
+     * that already specifies an edge keeps it: that viewer has already said how
+     * they want their captions separated from the picture.
+     *
+     * TRACES: UR-020 | DR-261
+     */
+    private fun captionStyle(): androidx.media3.ui.CaptionStyleCompat {
+        val base = try {
+            val captioning = appContext.getSystemService(Context.CAPTIONING_SERVICE)
+                as? android.view.accessibility.CaptioningManager
+            if (captioning != null && captioning.isEnabled) {
+                androidx.media3.ui.CaptionStyleCompat.createFromCaptionStyle(captioning.userStyle)
+            } else {
+                androidx.media3.ui.CaptionStyleCompat.DEFAULT
+            }
+        } catch (e: Exception) {
+            // A captioning service that refuses to answer is not a reason to
+            // draw nothing; fall back to the same default media3 would use.
+            android.util.Log.w("JellyTauPlayer", "Captioning preferences unavailable", e)
+            androidx.media3.ui.CaptionStyleCompat.DEFAULT
+        }
+
+        val needsOwnEdge = base.edgeType == androidx.media3.ui.CaptionStyleCompat.EDGE_TYPE_NONE
+
+        return androidx.media3.ui.CaptionStyleCompat(
+            base.foregroundColor,
+            android.graphics.Color.TRANSPARENT,
+            android.graphics.Color.TRANSPARENT,
+            if (needsOwnEdge) {
+                androidx.media3.ui.CaptionStyleCompat.EDGE_TYPE_OUTLINE
+            } else {
+                base.edgeType
+            },
+            if (needsOwnEdge) android.graphics.Color.BLACK else base.edgeColor,
+            base.typeface
+        )
+    }
+
     /**
      * The view that draws subtitle cues, for VideoOverlayManager to attach
      * directly above the video and below the WebView. Null before the first