docs: add Addy Osmani 80% problem to Practitioner Insights

Add Addy Osmani (Google Chrome Team) article "The 80% Problem in
Agentic Coding" to AI Ecosystem Practitioner Insights section.

Changes:
- guide/ai-ecosystem.md: Add 32-line entry after Steinberger (~line 2024)
  * "80% problem" framework and comprehension debt concept
  * Three new failure modes (overengineering, assumption propagation, sycophantic)
  * Productivity paradox data (+98% PRs, +91% review time)
  * Alignment table mapping to existing guide sections
  * Transparent note: "secondary synthesis, primary sources documented"

- machine-readable/reference.yaml: Add 4 new references
  * practitioner_addy_osmani, practitioner_osmani_source
  * eighty_percent_problem, comprehension_debt_secondary

- docs/resource-evaluations/024-addy-osmani-80-percent-problem.md: Complete evaluation
  * Score: 3/5 (Pertinent) - downgraded from initial 4/5 after technical-writer challenge
  * Minimal integration (32 lines vs rejected 250 lines)
  * Fact-check: 6 stats verified, 1 Stack Overflow stat incorrect
  * Rationale: 90% overlap with existing content (Vibe Coding Trap, Trust Calibration)

- CHANGELOG.md: Document addition in v3.19.0

Decision: Minimal integration approach chosen to avoid duplication while
recognizing value of synthesis from respected author. Article aggregates
existing research already cited in guide with primary sources.

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

guide/ai-ecosystem.md

@@ -2021,6 +2021,36 @@ External resources from experienced practitioners that validate and extend the p
 
 **Note**: Steinberger is the creator of Moltbot (see [ClawdBot FAQ](#claude-code-vs-clawdbot-whats-the-difference)). His observations originate from a non-Claude workflow; patterns should be validated in Claude Code context before adoption.
 
+### Addy Osmani (Google Chrome Team)
+
+**URL**: [The 80% Problem in Agentic Coding](https://addyo.substack.com/p/the-80-problem-in-agentic-coding)
+
+**Author credentials**:
+- Engineering leader at Google Chrome team
+- Bestselling author, 600K+ newsletter readers
+- Published January 28, 2026
+
+**Content summary**: Synthesis of the "80% problem" — when AI generates 80%+ of code, developers face three new failure modes (overengineering, assumption propagation, sycophantic agreement) and risk "comprehension debt" distinct from technical debt. Aggregates DORA, Stack Overflow, and industry research on the productivity paradox (+98% PRs, +91% review time, but no overall workload reduction).
+
+**Key data points** (cited from external research):
+- 44% developers write <10% code manually (Ronacher poll)
+- 48% only review AI code systematically before commit (SonarSource)
+- 66% frustrated with "almost right" AI solutions (Stack Overflow 2025)
+- 99% report 10+ hours saved weekly, yet no workload reduction (Atlassian 2025)
+
+**Alignment with this guide**:
+
+| Osmani Concept | This Guide Reference |
+|----------------|---------------------|
+| Comprehension debt | Vibe Coding Trap (learning-with-ai.md:81) |
+| Review as bottleneck | Trust Calibration (ultimate-guide.md:1061) |
+| Orchestrator role | Plan Mode + Task tool workflows |
+| +91% review time | Already cited (line 1977 above) |
+
+**Value**: Well-articulated synthesis introducing the "80% problem" framework. Useful secondary source for reinforcing concepts already documented in this guide with primary sources.
+
+**Note**: Article aggregates existing research. For primary data, see DORA Report 2025, Stack Overflow 2025, and Matteo Collina insights documented above.
+
 ---
 
 ## 11.3 Skills Distribution Platforms