lotus(#6): render decoration in MediaView; fix store lifecycle

Review found in-call tiles use MediaView->Avatar, not TileAvatar, so the
decoration never rendered in-call (CRITICAL). Move the overlay into
MediaView, gated on the avatar's own visibility (!(video && videoEnabled))
so it never floats over live video; revert the TileAvatar changes.
Also ref-count the io.lotus.decorations registration (one shared handler,
no double-reply) and stop clearing the map on teardown so a transient
remount doesn't drop decorations (HIGH/MED).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/tile/MediaView.module.css

@@ -61,6 +61,24 @@ Please see LICENSE in the repository root for full details.
   mix-blend-mode: multiply;
 }
 
+/* [lotus #6] Profile decoration overlaid on the tile avatar. Shares the
+avatar's centred box and size so frame-style decorations sit around it. */
+.lotusDecoration {
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  pointer-events: none;
+  object-fit: contain;
+}
+
+@container mediaView (width > 0) {
+  .lotusDecoration {
+    inline-size: 50cqmin;
+    block-size: 50cqmin;
+  }
+}
+
 /* CSS makes us put a condition here, even though all we want to do is
 unconditionally select the container so we can use cqmin units */
 @container mediaView (width > 0) {