docs: add research-backed documentation for v0.6.2

- Added docs/WHY.md with user-friendly rule explanations and authoritative sources
- Added docs/RESEARCH_CITATIONS.md with 551 lines of academic and industry references
- Updated README.md with micro-citations under each feature
- Enhanced CLI help with 'BACKED BY RESEARCH' section
- Updated AI tools mentions across all docs (GitHub Copilot, Cursor, Windsurf, Claude, ChatGPT, Cline)
- Organized documentation structure: moved RESEARCH_CITATIONS.md to docs/
- Version bump: 0.6.1 -> 0.6.2

Research backing includes:
- Academia: MIT Course 6.031, ScienceDirect studies
- Books: Clean Architecture (Martin 2017), DDD (Evans 2003)
- Industry: Google, Microsoft, Airbnb style guides, SonarQube
- Experts: Martin Fowler, Robert C. Martin, Eric Evans, Alistair Cockburn

packages/guardian/src/cli/constants.ts

@@ -28,7 +28,11 @@ export const CLI_DESCRIPTIONS = {
         "  🔴 CRITICAL - Must fix immediately (breaks architecture)\n" +
         "  🟠 HIGH     - Should fix soon (major quality issue)\n" +
         "  🟡 MEDIUM   - Should fix (moderate quality issue)\n" +
-        "  🟢 LOW      - Nice to fix (minor quality issue)",
+        "  🟢 LOW      - Nice to fix (minor quality issue)\n\n" +
+        "BACKED BY RESEARCH:\n" +
+        "  Guardian's rules are based on established software engineering principles\n" +
+        "  from MIT, Martin Fowler, Robert C. Martin, and industry standards.\n" +
+        "  Learn more: https://github.com/samiyev/puaros/blob/main/packages/guardian/docs/WHY.md",
     CHECK:
         "Analyze project for code quality and architecture issues\n\n" +
         "WORKFLOW:\n" +