Initial commit: E4B-MarkBase model integration with passing tests

- E4B-MarkBase model (42 layers, 4.4GB) loaded successfully
- All Phase 1-6 tests passed (model loading, forward pass, vision/audio towers, token generation, performance)
- All stress tests passed (5/5 in 127.6s)
  - Concurrent inference
  - Memory stress (67.5 tok/s, 0 NaN)
  - Continuous generation
  - Batch processing
  - Long-running stability
- Swift Metal inference engine with multimodal support

test31B.swift

@@ -0,0 +1,53 @@
+import Foundation
+import MarkBase
+
+let modelDir = "/Users/accusys/MarkBaseEngine/models/gemma-4-31b-it-4bit"
+
+guard FileManager.default.fileExists(atPath: modelDir + "/config.json") else {
+    print("✗ 31B model not found at \(modelDir)")
+    exit(1)
+}
+
+print("Loading engine...")
+let engine = try E4BEngine(autoCompile: true)
+print("✓ Engine created")
+
+print("\nLoading 31B model (~18 GB, may take 2-3 minutes)...")
+let model = try E4BModel(modelDir: modelDir, engine: engine, maxContextLength: 128)
+
+print("✓ Model loaded!")
+print("  Layers: \(model.numHiddenLayers)")
+print("  Hidden size: \(model.hiddenSize)")
+print("  Vocab size: \(model.vocabSize)")
+print("  Layer types: \(model.layerTypesIsFull.count) total, \(model.layerTypesIsFull.filter { $0 }.count) full, \(model.layerTypesIsFull.filter { !$0 }.count) sliding")
+
+print("\nLoading tokenizer...")
+let tokenizer = try TokenizerFactory.load(modelDir: modelDir)
+print("✓ Tokenizer loaded")
+
+// Test forward pass
+print("\n=== Forward pass test ===")
+let tokens = tokenizer.encode(text: "Hello")
+print("Tokenized 'Hello': \(tokens)")
+
+let logits = try model.forward(tokenId: tokens[0], position: 0)
+print("Forward pass complete: \(logits.count) logits")
+let maxLogit = logits.max() ?? -999
+print("Max logit: \(maxLogit)")
+
+let sorted = logits.enumerated().sorted { $0.element > $1.element }
+let top5 = sorted.prefix(5)
+print("Top 5 predictions:")
+for (idx, val) in top5 {
+    let tokenStr = tokenizer.decode(tokens: [idx])
+    print("  Token \(idx) ('\(tokenStr)'): \(val)")
+}
+
+// Generation test
+print("\n=== Generation test ===")
+let genConfig = GenerationConfig(maxTokens: 5, temperature: 0.7)
+let generator = StreamingGenerator(model: model, tokenizer: tokenizer, engine: engine)
+let response = try generator.generateComplete(prompt: "Hello", config: genConfig)
+print("Generated: '\(response)'")
+
+print("\n✅ 31B test complete!")