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

.claude/skills/trellis-before-dev/SKILL.md

@@ -0,0 +1,34 @@
+---
+name: trellis-before-dev
+description: "Discovers and injects project-specific coding guidelines from .trellis/spec/ before implementation begins. Reads spec indexes, pre-development checklists, and shared thinking guides for the target package. Use when starting a new coding task, before writing any code, switching to a different package, or needing to refresh project conventions and standards."
+---
+
+Read the relevant development guidelines before starting your task.
+
+Execute these steps:
+
+1. **Discover packages and their spec layers**:
+   ```bash
+   python3 ./.trellis/scripts/get_context.py --mode packages
+   ```
+
+2. **Identify which specs apply** to your task based on:
+   - Which package you're modifying (e.g., `cli/`, `docs-site/`)
+   - What type of work (backend, frontend, unit-test, docs, etc.)
+
+3. **Read the spec index** for each relevant module:
+   ```bash
+   cat .trellis/spec/<package>/<layer>/index.md
+   ```
+   Follow the **"Pre-Development Checklist"** section in the index.
+
+4. **Read the specific guideline files** listed in the Pre-Development Checklist that are relevant to your task. The index is NOT the goal — it points you to the actual guideline files (e.g., `error-handling.md`, `conventions.md`, `mock-strategies.md`). Read those files to understand the coding standards and patterns.
+
+5. **Always read shared guides**:
+   ```bash
+   cat .trellis/spec/guides/index.md
+   ```
+
+6. Understand the coding standards and patterns you need to follow, then proceed with your development plan.
+
+This step is **mandatory** before writing any code.