docs: add system prompts official sources (Anthropic + community analyses)

- Add System Prompt Contents section in architecture.md (line 300-326)
  - Official Anthropic sources (Tier 1, 100% confidence)
  - Community analyses (Simon Willison, PromptHub)
  - Claude.ai vs API vs Code CLI distinctions

- Update reference.yaml with 4 new system prompts entries
  - system_prompts_official, willison_analysis, prompthub, architecture

- Create resource evaluation: system-prompts-official-vs-community.md
  - Score evolution: 4/5 → 3/5 → 2/5 (after Perplexity fact-check)
  - Decision: Do not integrate x1xhlol repository (redundant)
  - Use official Anthropic sources instead

- Create watchlist for non-integrated resources
  - claudedocs/resource-evaluations/watch-list.md (gitignored)
  - Re-evaluation triggers: Q2 2026 or if 10+ user requests

Related evaluation: docs/resource-evaluations/system-prompts-official-vs-community.md

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

machine-readable/reference.yaml

@@ -89,6 +89,11 @@ deep_dive:
   architecture_mcp: "guide/architecture.md:506"
   architecture_mcp_visual: "guide/images/mcp-architecture-diagram.svg"
   architecture_philosophy: "guide/architecture.md:746"
+  # System Prompts (Official Sources) - Added 2026-01-26
+  system_prompts_official: "https://platform.claude.com/docs/en/release-notes/system-prompts"
+  system_prompts_willison_analysis: "https://simonwillison.net/2025/May/25/claude-4-system-prompt/"
+  system_prompts_prompthub: "https://www.prompthub.us/blog/an-analysis-of-the-claude-4-system-prompt"
+  system_prompts_architecture: "guide/architecture.md:299"
   # Main guide (guide/ultimate-guide.md) - Updated 2026-01-20
   installation: 196
   first_workflow: 277