Maximize GUI app window and fix input forwarding

- After window discovery, activate, move to (0,0), and resize to
  fill the 1280x1024 Xvfb display so the app is fullscreen
- Add windowactivate --sync before click events so the window
  receives focus in X11 before mouse input
- Add windowfocus --sync before key events so keyboard input
  goes to the correct window
- Make canvas fill the entire app panel area (width/height 100%)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/display.py

@@ -187,6 +187,8 @@ class ManagedGuiApp:
                     pass
             return
 
+        # Maximize the window to fill the Xvfb display and activate it
+        await self._maximize_window()
         log.info("Capture loop started for app %s window %d", self.app_id, self.window_id)
 
         while self.alive:
@@ -357,6 +359,25 @@ class ManagedGuiApp:
             grandchildren.extend(ManagedGuiApp._get_descendant_pids(cpid))
         return children + grandchildren
 
+    async def _maximize_window(self):
+        """Activate the window, resize it to fill the Xvfb display, and move to origin."""
+        if not self.window_id or not XDOTOOL_BIN:
+            return
+        env = self._display_env()
+        wid = str(self.window_id)
+        try:
+            # Activate (focus) the window
+            await self._xdotool("windowactivate", "--sync", wid, env=env)
+            # Move to origin
+            await self._xdotool("windowmove", "--sync", wid, "0", "0", env=env)
+            # Resize to fill display (Xvfb is 1280x1024)
+            await self._xdotool("windowsize", "--sync", wid, "1280", "1024", env=env)
+            # Some apps need a moment to redraw after resize
+            await asyncio.sleep(0.3)
+            log.debug("Maximized window %s to 1280x1024 for %s", wid, self.app_id)
+        except Exception as e:
+            log.debug("Failed to maximize window %s: %s", wid, e)
+
     async def _xdotool_search(self, *args, env=None) -> Optional[int]:
         """Run xdotool search and return first window ID, or None."""
         try:
@@ -399,6 +420,7 @@ class ManagedGuiApp:
         if action == "click":
             btn = str(msg.get("button", 1))
             await self._xdotool(
+                "windowactivate", "--sync", wid,
                 "mousemove", "--window", wid, x, y,
                 "click", "--window", wid, btn,
                 env=env,
@@ -406,6 +428,7 @@ class ManagedGuiApp:
         elif action == "dblclick":
             btn = str(msg.get("button", 1))
             await self._xdotool(
+                "windowactivate", "--sync", wid,
                 "mousemove", "--window", wid, x, y,
                 "click", "--window", wid, "--repeat", "2", btn,
                 env=env,
@@ -449,7 +472,11 @@ class ManagedGuiApp:
 
         wid = str(self.window_id)
         if action == "press":
-            await self._xdotool("key", "--window", wid, xkey, env=env)
+            await self._xdotool(
+                "windowfocus", "--sync", wid,
+                "key", "--window", wid, xkey,
+                env=env,
+            )
         # release events handled implicitly by xdotool key
 
     async def _xdotool(self, *args, env=None):

frontend/css/apps/display.css

@@ -9,18 +9,17 @@
 .gui-canvas-wrap {
     flex: 1;
     display: flex;
-    align-items: center;
-    justify-content: center;
     overflow: hidden;
     position: relative;
 }
 
 .gui-canvas {
-    max-width: 100%;
-    max-height: 100%;
+    width: 100%;
+    height: 100%;
     cursor: default;
     outline: none;
     image-rendering: auto;
+    object-fit: contain;
 }
 
 /* Status overlays */