chore(ui): remove dead Mission Control monitor-pane stack

Auto-seeding of monitor tiles was disabled in 724814f; Mission Control now
only shows ConPTY panes. Removes Monitors/EnsureMonitor/SeedActive, the
detach/re-dock machinery, MonitorPaneView and the detached monitor window,
plus their tests and orphaned localization keys.

TaskMonitorViewModel itself stays: DetailsIslandViewModel still uses it as
the backing state for the task Log/AgentState/AskUser-question UI, so only
its Mission-Control-only members (Title/DisplayTitle, detach, cancel command,
IMissionControlPane) were stripped. IMissionControlPane/Panes were kept
(now a 1:1 mirror of ConPtySessions) rather than dissolved, to avoid
churning the still-live ConPTY pane tests and AXAML for a single-implementer
interface.

Visual verification still open: Mission Control with several open ConPTY
tiles, and the Focus/Overview toggle.

src/ClaudeDo.Ui/Views/Islands/DetailsIslandView.axaml

@@ -81,8 +81,7 @@
             </StackPanel>
           </Border>
 
-          <!-- Question prompt (AskUser): answer the running task's question inline, mirroring
-               the Mission Control banner. State is shared via the same TaskMonitorViewModel. -->
+          <!-- Question prompt (AskUser): answer the running task's question inline. -->
           <Border DockPanel.Dock="Top"
                   IsVisible="{Binding Monitor.HasPendingQuestion}"
                   Margin="0,0,0,10" Padding="12,8"