feat: add multi-item ingest and Reed-Solomon parity

- Multi-item ingest: each item gets its own Unix socket, Rust processes
  them sequentially into a single snapshot with separate chunk lists
- Reed-Solomon parity: rs(20,1) erasure coding for pack file groups,
  enabling single-pack-loss recovery via parity reconstruction
- Repair now attempts parity-based recovery for missing pack files
- 16 integration tests + 12 Rust unit tests all pass

ts/classes.containerarchive.ts

@@ -150,24 +150,70 @@ export class ContainerArchive {
 
   /**
    * Ingest multiple data streams as a single multi-item snapshot.
+   * Each item gets its own Unix socket for parallel data transfer.
    */
   async ingestMulti(
     items: IIngestItem[],
     options?: IIngestOptions,
   ): Promise<ISnapshot> {
-    // For multi-item, we concatenate all streams into one socket
-    // and pass item metadata so Rust can split them.
-    // For now, we implement a simple sequential approach:
-    // ingest first item only (multi-item will be enhanced later).
     if (items.length === 0) {
       throw new Error('At least one item is required');
     }
 
-    const firstItem = items[0];
-    return this.ingest(firstItem.stream, {
-      ...options,
-      items: items.map((i) => ({ name: i.name, type: i.type || 'data' })),
-    });
+    // Create one socket per item
+    const sockets: Array<{
+      socketPath: string;
+      promise: Promise<void>;
+      server: plugins.net.Server;
+    }> = [];
+
+    const itemOptions: Array<{
+      name: string;
+      type: string;
+      socketPath: string;
+    }> = [];
+
+    try {
+      for (const item of items) {
+        const socketPath = plugins.path.join(
+          plugins.os.tmpdir(),
+          `containerarchive-ingest-${Date.now()}-${Math.random().toString(36).slice(2)}.sock`,
+        );
+
+        const { promise, server } = await this.createSocketServer(socketPath, item.stream);
+        sockets.push({ socketPath, promise, server });
+        itemOptions.push({
+          name: item.name,
+          type: item.type || 'data',
+          socketPath,
+        });
+      }
+
+      // Send ingestMulti command to Rust with per-item socket paths
+      const result = await this.bridge.sendCommand('ingestMulti', {
+        tags: options?.tags,
+        items: itemOptions,
+      });
+
+      // Wait for all data transfers
+      await Promise.all(sockets.map((s) => s.promise));
+
+      const snapshot = result.snapshot;
+      this.ingestComplete.next({
+        snapshotId: snapshot.id,
+        originalSize: snapshot.originalSize,
+        storedSize: snapshot.storedSize,
+        newChunks: snapshot.newChunks,
+        reusedChunks: snapshot.reusedChunks,
+      });
+
+      return snapshot;
+    } finally {
+      for (const s of sockets) {
+        s.server.close();
+        try { plugins.fs.unlinkSync(s.socketPath); } catch {}
+      }
+    }
   }
 
   /**