fix: move ViewToggle into header bars and remove subtitle

Eliminates the dedicated ViewToggle row on CockpitPage by merging
it into IncidentHeader's action group via extraActions prop. Removes
subtitle from ViewToggle component entirely — the icon + label is
self-explanatory. Cleans up showSubtitle prop from all call sites.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/FlowPilotPage.tsx

@@ -116,7 +116,7 @@ export default function FlowPilotPage() {
                 </button>
                 <div className="flex-1" />
                 {session.activeChatId && (
-                  <ViewToggle currentView="flowpilot" sessionId={session.activeChatId} showSubtitle={false} />
+                  <ViewToggle currentView="flowpilot" sessionId={session.activeChatId} />
                 )}
                 <button
                   onClick={session.handleNewChat}