Desktop session batch 09-12: frameless chrome, bisect removal, chat/idle fixes

Frameless (window_manager, hidden titlebar): chrome bar on welcome,
drag-to-move appbar + window buttons on connect, drag layer + window
buttons in session controls; min size 160x90; volume-scroll off for
drag; session maximize = fullscreen toggle. Verified on KDE Wayland.
Delete legacy/minimal/nosheet bisect screens; session routes direct
(black-screen fix verified incl. WAN).
Avatar: pipeline now 128px aspect-kept PNG (was cropped JPEG);
profile card centered 64px hover-to-change; member avatar drops
ResizeImage downscale. NOTE open: pipeline 512 KiB check vs server
64 KiB enforcement mismatch.
Fixes: idle warn/unready skipped while PLAYING; sendChat drops
blanks; one chat row per send (drop textless server feed echo);
chat field keeps focus after send. Playback libass true; sdk floor
3.13. Handoff 9-11: 9+10 fixed, 11 jumpy seek still open.
Docs: handoff/roadmap/protocol record all of the above; few-commits
preference going forward.

apps/desktop/lib/src/widgets/member_avatar.dart

@@ -9,12 +9,7 @@ class MemberAvatar extends StatelessWidget {
 
   static final Map<String, MemoryImage> _images = {};
 
-  const MemberAvatar({
-    super.key,
-    required this.avatarBase64,
-    required this.name,
-    this.size = 40,
-  });
+  const MemberAvatar({super.key, required this.avatarBase64, required this.name, this.size = 40});
 
   static MemoryImage? _providerFor(String raw) {
     if (raw.isEmpty) return null;
@@ -33,15 +28,13 @@ class MemberAvatar extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final image = _providerFor(avatarBase64);
-    final decoration = BoxDecoration(
-      shape: BoxShape.circle,
-    );
+    final decoration = BoxDecoration(shape: BoxShape.circle);
     if (image != null) {
       return Container(
         decoration: decoration,
         child: ClipOval(
           child: Image(
-            image: ResizeImage(height: (size * MediaQuery.of(context).devicePixelRatio).round(), image),
+            image: image,
             width: size,
             height: size,
             fit: BoxFit.cover,
@@ -55,11 +48,11 @@ class MemberAvatar extends StatelessWidget {
   }
 
   Widget _fallback() => CircleAvatar(
-        radius: size / 2,
-        backgroundColor: Colors.grey.shade800,
-        child: Text(
-          name.isEmpty ? '?' : name[0].toUpperCase(),
-          style: TextStyle(fontSize: size * 0.4, color: Colors.white),
-        ),
-      );
+    radius: size / 2,
+    backgroundColor: Colors.grey.shade800,
+    child: Text(
+      name.isEmpty ? '?' : name[0].toUpperCase(),
+      style: TextStyle(fontSize: size * 0.4, color: Colors.white),
+    ),
+  );
 }