Fix Buffer to ArrayBuffer conversion using proper allocation

Create new ArrayBuffer and copy Buffer data using Uint8Array.set()
to avoid SharedArrayBuffer type issues.

Fixes: Type 'ArrayBuffer | SharedArrayBuffer' is not assignable to type 'ArrayBuffer'

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

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: sallyom

components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/workspace/upload/route.ts

@@ -84,8 +84,11 @@ async function compressImageIfNeeded(
       `Compressed image: ${buffer.byteLength} bytes -> ${compressed.byteLength} bytes (${Math.round((compressed.byteLength / buffer.byteLength) * 100)}%)`
     );
 
-    // Convert Buffer to ArrayBuffer
-    return compressed.buffer.slice(compressed.byteOffset, compressed.byteOffset + compressed.byteLength);
+    // Convert Node.js Buffer to ArrayBuffer by creating a new ArrayBuffer and copying data
+    const arrayBuffer = new ArrayBuffer(compressed.byteLength);
+    const view = new Uint8Array(arrayBuffer);
+    view.set(compressed);
+    return arrayBuffer;
   } catch (error) {
     console.error('Failed to compress image:', error);
     // If compression fails, throw error rather than uploading oversized file