feat: Add new skills and templates for domain modeling, bug diagnosis, and architectural improvement

- Introduced a human-in-the-loop script for bug diagnosis to capture user feedback.
- Created ADR and CONTEXT formats to standardize architectural decision records and domain context documentation.
- Developed a domain modeling skill to refine terminology and maintain a shared language.
- Enhanced the improve-codebase-architecture skill to provide visual reports and deepening opportunities.
- Consolidated grilling and handoff skills for better user interaction and documentation.
- Updated existing skills to improve clarity and consistency in descriptions and functionality.

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "mattpocock-skills",
   "skills": [
-    "./skills/engineering/diagnose",
+    "./skills/engineering/diagnosing-bugs",
     "./skills/engineering/grill-with-docs",
     "./skills/engineering/triage",
     "./skills/engineering/improve-codebase-architecture",
@@ -11,8 +11,11 @@
     "./skills/engineering/to-prd",
     "./skills/engineering/zoom-out",
     "./skills/engineering/prototype",
+    "./skills/engineering/domain-modeling",
+    "./skills/engineering/codebase-design",
     "./skills/productivity/caveman",
     "./skills/productivity/grill-me",
+    "./skills/productivity/grilling",
     "./skills/productivity/handoff",
     "./skills/productivity/teach",
     "./skills/productivity/write-a-skill"