feat(swift): implementeer artifact lifecycle management (E4.S2)

Epic 4 Story 2 compleet: Meerdere artifacts met open/close/switch werken!

E4.S2 - Artifact Lifecycle Management (3 SP)
- Store state: openArtifacts[], activeArtifactId
- Store actions met max 3 artifacts logica
- ArtifactArea refactor naar ArtifactContainer
- CommandCenter integration met nieuwe artifact system

Store Updates (stores/swift-store.ts):
- openArtifacts: Artifact[] — Array van open artifacts
- activeArtifactId: string | null — Currently active artifact
- Initial state: [], null

Store Actions:
```typescript
openArtifact(artifact: Omit<Artifact, 'id' | 'createdAt'>) {
  // Auto-generate ID + timestamp
  // Max 3 artifacts: remove oldest if at capacity
  // Set new artifact as active
}

closeArtifact(id: string) {
  // Filter out artifact
  // Auto-switch to last remaining if closing active
}

switchArtifact(id: string) {
  // Verify artifact exists
  // Set activeArtifactId
}

closeAllArtifacts() {
  // Clear all artifacts + active ID
}
```

Features:
- Max 3 artifacts enforced (oldest removed at capacity)
- Auto-switch when closing active artifact
- Console logging voor debugging
- ID generation met crypto.randomUUID()
- Timestamp tracking met createdAt

Components Updated:
- components/swift/artifacts/artifact-area.tsx (30 regels)
  - Simplified: alleen ArtifactContainer rendering
  - Props: openArtifacts, activeArtifactId, switchArtifact, closeArtifact

- components/swift/command-center/command-center.tsx
  - openArtifact() i.p.v. openBlock()
  - getArtifactTitle() voor dynamic titles
  - Escape: closeAllArtifacts() i.p.v. closeBlock()
  - Artifact opening met title generation

Integration Flow:
1. Chat: AI genereert action met artifact data
2. ChatPanel: setPendingAction(action)
3. CommandCenter: useEffect detecteert pendingAction
4. CommandCenter: getArtifactTitle(type, prefill)
5. CommandCenter: openArtifact({ type, prefill, title })
6. Store: Auto-generate ID, check max 3, add to array
7. ArtifactArea: Renders ArtifactContainer met artifacts
8. ArtifactContainer: Shows tabs (if >1), renders active block

Console Logging:
- "[Store] Max 3 artifacts reached, removing oldest"
- "[Store] Opening artifact: dagnotitie Dagnotitie - Jan"
- "[Store] Closing artifact: [id] New active: [id]"
- "[Store] Switching to artifact: [id]"
- "[Store] Cannot switch to artifact: [id] (not found)"

Build Status:
- ✅ pnpm build succesvol (geen type errors)
- Alleen bekende warnings (Supabase realtime, useCallback)

Voortgang: 56 SP / 85 SP (66%) - 18/31 stories compleet, 2 geskipt

Next: E4.S3 (Slide-in animatie) - 200ms ease-out transitions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

components/swift/command-center/command-center.tsx

@@ -22,18 +22,19 @@ import { ContextBar } from './context-bar';
 import { OfflineBanner } from './offline-banner';
 import { ChatPanel } from '../chat/chat-panel';
 import { ArtifactArea } from '../artifacts/artifact-area';
+import { getArtifactTitle } from '../artifacts/artifact-container';
 
 export function CommandCenter() {
-  const { closeBlock, activeBlock, openBlock, pendingAction, setPendingAction } = useSwiftStore();
+  const { closeAllArtifacts, openArtifacts, openArtifact, pendingAction, setPendingAction } = useSwiftStore();
   const inputRef = useRef<HTMLInputElement>(null);
 
   // Global keyboard shortcuts
   const handleKeyDown = useCallback(
     (e: KeyboardEvent) => {
-      // Escape: close active block
-      if (e.key === 'Escape' && activeBlock) {
+      // Escape: close all artifacts
+      if (e.key === 'Escape' && openArtifacts.length > 0) {
         e.preventDefault();
-        closeBlock();
+        closeAllArtifacts();
       }
 
       // Cmd/Ctrl + K: focus input (chat input in v3.0)
@@ -42,7 +43,7 @@ export function CommandCenter() {
         inputRef.current?.focus();
       }
     },
-    [activeBlock, closeBlock]
+    [openArtifacts, closeAllArtifacts]
   );
 
   useEffect(() => {
@@ -50,7 +51,7 @@ export function CommandCenter() {
     return () => window.removeEventListener('keydown', handleKeyDown);
   }, [handleKeyDown]);
 
-  // E3.S6: Handle pending actions from chat (artifact opening)
+  // E3.S6 + E4.S2: Handle pending actions from chat (artifact opening)
   useEffect(() => {
     if (!pendingAction) return;
 
@@ -60,10 +61,17 @@ export function CommandCenter() {
     if (pendingAction.artifact) {
       const { type, prefill } = pendingAction.artifact;
 
-      console.log('[CommandCenter] Opening artifact:', type, 'with prefill:', prefill);
+      // Generate title for the artifact
+      const title = getArtifactTitle(type, prefill);
 
-      // Open the block with prefill data
-      openBlock(type, prefill);
+      console.log('[CommandCenter] Opening artifact:', type, title);
+
+      // Open the artifact (E4.S2 - new artifact system)
+      openArtifact({
+        type,
+        prefill,
+        title,
+      });
 
       // Clear pending action after processing
       setPendingAction(null);
@@ -71,7 +79,7 @@ export function CommandCenter() {
       console.log('[CommandCenter] Action has no artifact, skipping');
       setPendingAction(null);
     }
-  }, [pendingAction, openBlock, setPendingAction]);
+  }, [pendingAction, openArtifact, setPendingAction]);
 
   return (
     <div className="flex flex-col h-screen overflow-hidden">