Add display mode chooser and align screen-sharing styles

Open the four display modes from XF86Display or the external-monitor bar icon. Reuse output reconciliation and confirmation for manual layout changes, and notify the shell when monitor state changes.

Release backdrop locks before render-element queries to prevent blurred popups from freezing the compositor. Cover popup open, update and close with regression tests.

Share translucent card styles between display modes and capture sources, show focus rings during keyboard navigation, and align picker buttons, label sizing and footer spacing with system modals.

protocols/ferese-shell-v1.xml

@@ -22,7 +22,7 @@
     DEALINGS IN THE SOFTWARE.
   </copyright>
 
-  <interface name="ferese_shell_manager_v1" version="5">
+  <interface name="ferese_shell_manager_v1" version="6">
     <description summary="create a capability-scoped Ferese shell controller">
       This private global is visible only to clients granted the shell-control
       capability. It does not assign a Wayland surface role.
@@ -35,7 +35,7 @@
     <request name="destroy" type="destructor"/>
   </interface>
 
-  <interface name="ferese_shell_v1" version="5">
+  <interface name="ferese_shell_v1" version="6">
     <description summary="managed-window metadata and shell control">
       Window, workspace, and output identifiers are unsigned 64-bit values
       encoded as high and low 32-bit words. Each snapshot atomically replaces
@@ -171,5 +171,15 @@
       </description>
       <arg name="output_name" type="string"/>
     </event>
+    <event name="toggle_display_mode" since="6">
+      <description summary="toggle the display mode chooser on the focused output"/>
+      <arg name="output_name" type="string"/>
+    </event>
+    <event name="monitor_state_changed" since="6">
+      <description summary="physical monitor configuration changed">
+        Query the output IPC inventory after reconciliation. This includes
+        disabled monitors and mirror targets without a logical wl_output.
+      </description>
+    </event>
   </interface>
 </protocol>