docs: add Addy Osmani spec-writing evaluation (4/5) + spec-first.md sections

Integration of "How to write a good spec for AI agents" by Addy Osmani:

Evaluation (docs/resource-evaluations/addy-osmani-good-spec.md):
- Score: 4/5 (High Value - Integrate within 1 week)
- Fills gaps: modular design, operational boundaries, command specs
- Fact-checked: credentials verified via Perplexity, all claims sourced
- Challenge phase: technical-writer agent corrected initial 3/5 → 4/5

Spec-First Workflow Updates (guide/workflows/spec-first.md):
- NEW: "Modular Spec Design" section (~50 lines, line 322)
  Pattern: Split large specs into focused files (CLAUDE-[domain].md)
- NEW: "Operational Boundaries" section (~60 lines, line 372)
  Three-tier system: Always/Ask First/Never → maps to Claude Code modes
- NEW: "Command Spec Template" section (~40 lines, line 432)
  Executable command specs with expected outputs & error handling
- NEW: "Anti-Pattern: Monolithic CLAUDE.md" section (~30 lines, line 472)
  Explains cognitive load problem (>200 lines = context pollution)

Reference Index (machine-readable/reference.yaml):
- 8 new entries: spec_first_workflow → spec_osmani_score
- Links to new spec-first.md sections with line numbers
- Source attribution: https://addyosmani.com/blog/good-spec/

Public Facing (README.md):
- Incremented resource evaluations count: 35 → 36

File growth: spec-first.md 327 → 507 lines (+180)
Source: Addy Osmani (former Chrome team, 14y), published Jan 13, 2026

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

README.md

@@ -424,7 +424,7 @@ cd quiz && npm install && npm start
 </details>
 
 <details>
-<summary><strong>Resource Evaluations</strong> (35 assessments)</summary>
+<summary><strong>Resource Evaluations</strong> (36 assessments)</summary>
 
 Systematic evaluation of external resources (tools, methodologies, articles) before integration into the guide.