Add runtime_config.json with optimal spec decode settings

runtime_config.json

@@ -0,0 +1,35 @@
+{
+    "_comment": "Optimal runtime configuration for TokForge speculative decoding",
+    "recommended": {
+        "target_backend": "opencl",
+        "draft_backend": "cpu",
+        "draft_predict_length": 3,
+        "draft_thread_num": 2,
+        "draft_power": "high",
+        "draft_sampler_type": "greedy"
+    },
+    "compatible_targets": {
+        "qwen3_8b": {
+            "enabled": true,
+            "uplift": "+24-40% (3x avg, 500-tok prose)"
+        },
+        "qwen3_14b": {
+            "enabled": true,
+            "uplift": "+40-70% (3x avg, 500-tok prose)"
+        },
+        "qwen3_4b": {
+            "enabled": false,
+            "reason": "Degenerates — KL trained from 8B teacher"
+        },
+        "qwen3_5": {
+            "enabled": false,
+            "reason": "Not compatible — different architecture (LinearAttention)"
+        }
+    },
+    "notes": {
+        "thread_num": "2 threads keeps WALT governor on performance cores. 4+ threads spread load and governor drops to min frequency.",
+        "power_high": "Forces Android performance hint. Critical for draft model speed.",
+        "draft_backend_cpu": "CPU draft avoids GPU memory contention with OpenCL target. OpenCL draft OOMs on 16GB devices.",
+        "predict_length_3": "d=3 is optimal across all tested devices. d=2 too conservative, d=4 wastes draft overhead."
+    }
+}