feat(web): add an open-monitoring-column button to the server list

When a server is connected, has monitor screens to show, and the monitoring
column isn't open, show an "open monitoring column" button to the right of the
list expand/collapse toggle on the server list. It reuses PinColumnButton (the
same right-sidebar affordance the monitor screens use, now with an optional
label), so opening the column is reachable from the server list — not only from
a monitor screen's pin button. InspectorView gates it on
`canPin && monitorAvailable.length > 0 && !effectivePinned`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BrihGWcrM9JGRyu41nzZYw

clients/web/src/components/views/InspectorView/InspectorView.tsx

@@ -850,6 +850,10 @@ export function InspectorView({
   // column. Gated by `canPin` so the pin affordance only appears when a click
   // would actually take effect (wide + connected).
   const canPin = !!isWide && connected;
+  // Offer an "open monitoring column" affordance on the server list when a
+  // connected server has monitor screens to show but the column isn't open yet.
+  const canOpenMonitor =
+    canPin && monitorAvailable.length > 0 && !effectivePinned;
   function pinMonitor(tab: MonitorTab) {
     setMonitorTab(tab);
     setMonitorPinned(true);
@@ -1068,6 +1072,11 @@ export function InspectorView({
                 onClearHighlight={onClearHighlight}
                 compact={serversCompact}
                 onToggleCompact={() => setServersCompact((c) => !c)}
+                onOpenMonitor={
+                  canOpenMonitor
+                    ? () => pinMonitor(effectiveMonitorTab)
+                    : undefined
+                }
               />
             </ScreenStage>
             <ScreenStage active={activeTab === "Tools"}>