feat(ST-1369): SprintSwitcher op deriveScreenState + draft op trigger (G5)

De trigger-knop toont nu de concept-sprint zodra er een sprint-draft loopt,
niet langer alleen de (disabled) dropdown-regel. Schermstaat-afleiding loopt
via de pure deriveScreenState() i.p.v. losse flags.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/shared/sprint-switcher.tsx

@@ -18,6 +18,7 @@ import {
   switchActiveSprintAction,
 } from '@/actions/active-sprint'
 import { useProductWorkspaceStore } from '@/stores/product-workspace/store'
+import { deriveScreenState } from '@/stores/product-workspace/screen-state'
 import { useUserSettingsStore } from '@/stores/user-settings/store'
 import type { SprintStatusApi } from '@/lib/task-status'
 import { debugProps } from '@/lib/debug'
@@ -57,6 +58,20 @@ export function SprintSwitcher({
   const draftGoal = useUserSettingsStore(
     (s) => s.entities.settings.workflow?.pendingSprintDraft?.[productId]?.goal ?? null,
   )
+  const pendingAdds = useProductWorkspaceStore(
+    (s) => s.sprintMembership.pending.adds,
+  )
+  const pendingRemoves = useProductWorkspaceStore(
+    (s) => s.sprintMembership.pending.removes,
+  )
+
+  const screenState = deriveScreenState({
+    activeSprintItem: activeSprint,
+    buildingSprintIds,
+    hasPendingDraft: draftGoal !== null,
+    pendingAdds,
+    pendingRemoves,
+  })
 
   const visibleSprints = sprints.filter(s => {
     if (showClosed) return true
@@ -139,10 +154,19 @@ export function SprintSwitcher({
         disabled={isPending}
         className="flex items-center gap-1.5 text-sm text-muted-foreground hover:text-foreground transition-colors px-2 py-1 rounded-md hover:bg-surface-container focus:outline-none"
       >
-        <span className="truncate max-w-[160px]">
-          {activeSprint ? activeSprint.code : 'Selecteer sprint'}
+        <span
+          className={cn(
+            'truncate max-w-[160px]',
+            screenState.kind === 'DRAFT' && 'italic text-tertiary',
+          )}
+        >
+          {screenState.kind === 'DRAFT'
+            ? `⚙ Concept — ${draftGoal}`
+            : activeSprint
+              ? activeSprint.code
+              : 'Selecteer sprint'}
         </span>
-        {activeSprint && (
+        {screenState.kind !== 'DRAFT' && activeSprint && (
           <span
             className={cn(
               'text-sm',