v2: add EmbeddingKernels to Metal compilation pipeline

Package.swift

@@ -17,7 +17,7 @@ let package = Package(
     targets: [
         .target(
             name: "MarkBase",
-            exclude: ["Metal/MetalKernels.metal", "Metal/OptimizedKernels.metal", "Metal/FusionKernels.metal", "Metal/MetalKernels.metallib", "Metal/metallib"],
+            exclude: ["Metal/MetalKernels.metal", "Metal/OptimizedKernels.metal", "Metal/FusionKernels.metal", "Metal/EmbeddingKernels.metal", "Metal/MetalKernels.metallib", "Metal/metallib"],
             linkerSettings: [
                 .linkedFramework("Metal"),
                 .linkedFramework("Foundation"),

Sources/MarkBase/MetalKernels.swift

@@ -109,6 +109,21 @@ public enum MetalKernels {
             .replacingOccurrences(of: "using namespace metal;\n", with: "")
         result += "\n" + fusedStripped
         
+        // Strip preamble from embedding kernels source
+        let embStripped = embeddingKernelsSource
+            .replacingOccurrences(of: "#include <metal_stdlib>\n", with: "")
+            .replacingOccurrences(of: "using namespace metal;\n", with: "")
+        result += "\n" + embStripped
+        
         return result
     }
-}
+
+    /// Embedding kernel source for EmbeddingGemma.
+    /// Includes RoPE, bidirectional sliding window attention, Q/K norm, and GELU.
+    public static var embeddingKernelsSource: String {
+        let url = URL(fileURLWithPath: #filePath)
+            .deletingLastPathComponent()
+            .appendingPathComponent("Metal/EmbeddingKernels.metal")
+        return try! String(contentsOf: url, encoding: .utf8)
+    }
+}