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

.trellis/spec/backend/logging-guidelines.md

@@ -0,0 +1,51 @@
+# Logging Guidelines
+
+> How logging is done in this project.
+
+---
+
+## Overview
+
+<!--
+Document your project's logging conventions here.
+
+Questions to answer:
+- What logging library do you use?
+- What are the log levels and when to use each?
+- What should be logged?
+- What should NOT be logged (PII, secrets)?
+-->
+
+(To be filled by the team)
+
+---
+
+## Log Levels
+
+<!-- When to use each level: debug, info, warn, error -->
+
+(To be filled by the team)
+
+---
+
+## Structured Logging
+
+<!-- Log format, required fields -->
+
+(To be filled by the team)
+
+---
+
+## What to Log
+
+<!-- Important events to log -->
+
+(To be filled by the team)
+
+---
+
+## What NOT to Log
+
+<!-- Sensitive data, PII, secrets -->
+
+(To be filled by the team)