feat(ui): keep the active operations tab across page refreshes (#27)

Persist the selected tab ID to localStorage (sw-active-tab) on every change
and restore it on mount when it matches one of the seven valid tab IDs. The
Radix Tabs become controlled for this; SSR and first client render still agree
on the default, so there is no hydration mismatch.

components/mission-control.tsx

@@ -38,6 +38,11 @@ function useNarrow(threshold = 900): boolean {
   return narrow
 }
 
+// Must match the TabsTrigger values in the render below — used to validate the tab persisted for
+// #27 (an unknown stored value falls back to the default).
+const TAB_IDS = ['world-map', 'local-system', 'crew', 'ship-systems', 'skill-tree', 'missions', 'event-log']
+const ACTIVE_TAB_KEY = 'sw-active-tab'
+
 export function MissionControl() {
   const narrow = useNarrow()
   const [tick, setTick] = useState(0)
@@ -49,6 +54,9 @@ export function MissionControl() {
   const [system, setSystem] = useState<SystemState | null>(null)
   const [techs, setTechs] = useState<TechDto[] | null>(null)
   const [crewCount, setCrewCount] = useState<number | null>(null)
+  // #27 — the active tab survives a page refresh. Restored from localStorage on mount; null until
+  // then so SSR and the first client render agree on the default tab (no hydration mismatch).
+  const [activeTab, setActiveTab] = useState<string | null>(null)
 
   useEffect(() => {
     let cancelled = false
@@ -98,6 +106,12 @@ export function MissionControl() {
     return () => clearInterval(id)
   }, [])
 
+  // #27 — restore the persisted tab once on mount (validated against TAB_IDS).
+  useEffect(() => {
+    const stored = window.localStorage.getItem(ACTIVE_TAB_KEY)
+    if (stored && TAB_IDS.includes(stored)) setActiveTab(stored)
+  }, [])
+
   const timeStr = new Date().toLocaleTimeString('en-GB', { hour12: false })
 
   // Slugs of the researched techs — drives the effective caps + build gates in the SHIP SYSTEMS
@@ -356,7 +370,13 @@ export function MissionControl() {
               </PanelHeader>
 
               <PanelContent style={{ padding: 0, flex: 1, minHeight: 0, overflowY: 'auto' }}>
-                <Tabs defaultValue="world-map">
+                <Tabs
+                  value={activeTab ?? 'world-map'}
+                  onValueChange={(v) => {
+                    setActiveTab(v)
+                    window.localStorage.setItem(ACTIVE_TAB_KEY, v) // #27 — keep the tab across refreshes
+                  }}
+                >
                   <TabsList
                     style={{
                       padding: '0 1rem',