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.Localization/locales/en.json

@@ -266,13 +266,8 @@
     "reviewResetTip": "Discard all changes and reset the task to Idle"
   },
   "missionControl": {
-    "openInApp": "Open in app",
-    "cancel": "Cancel",
-    "detach": "Detach",
-    "redock": "Re-dock",
     "windowTitle": "Mission Control",
     "newSession": "New session",
-    "clearFinished": "Clear finished",
     "empty": "No running tasks",
     "settings": "Settings",
     "queue": "Queue",