feat: init mlkem project with Verilator test framework

- sync_rtl/common/: skid_buffer, pipeline_reg, defines (valid/ready)
- sync_rtl/mod_add/: modular adder example with Verilator C++ TB
- test_framework/: Python-driven Verilator compile/sim/compare pipeline
- test_framework/modules/mod_add/: 50-vector test plan, full鏈路 PASS
- .trellis/spec/: RTL and test_framework conventions documented

test_framework/config.json

@@ -0,0 +1,12 @@
+{
+  "verilator": {
+    "path": "verilator",
+    "compile_args": ["-Wall", "--cc", "--build", "--timing", "--exe"]
+  },
+  "clock_period_ns": 10.0,
+  "timeout_cycles": 100000,
+  "rtl_root": "sync_rtl",
+  "vector_root": "test_framework/modules/{module}/vectors",
+  "report_root": "test_framework/reports",
+  "keep_vectors": false
+}