docs: add AI productivity research, trust calibration, and exploration workflow

## New Content

### Trust & Verification (ultimate-guide.md)
- Section 1.7 "Trust Calibration: When and How Much to Verify" (~155 lines)
  - Research-backed stats (ACM, Veracode, CodeRabbit, Cortex.io)
  - Verification spectrum by code type
  - Solo vs Team strategies with workflow diagrams
  - "Prove It Works" checklist
- New pitfall: "Trust AI output without proportional verification"
- CLAUDE.md size guideline: 4-8KB optimal, >16K degrades coherence

### AI Productivity (learning-with-ai.md)
- Section "The Reality of AI Productivity" (~55 lines)
  - Productivity curve phases (Wow Effect → Targeted Gains → Plateau)
  - High-gain vs low/negative-gain task categorization
  - Team success factors
- Productivity trajectory table by pattern (Dependent/Avoidant/Augmented)
- 5 new sources (GitHub, McKinsey, Stack Overflow, Uplevel, DORA)

### Session Limits (architecture.md)
- "Session Degradation Limits" section
  - Turn limits (15-25), token thresholds (80-100K)
  - Success rates by scope (1-3 files: ~85%, 8+ files: ~40%)

### Exploration Workflow
- NEW: guide/workflows/exploration-workflow.md
  - Anti-anchoring prompts, 3-5 approaches pattern
- iterative-refinement.md: Script Generation Workflow (3-7 iteration pattern)
- anchor-catalog.md: Anti-Anchoring Techniques, Exploration/Iteration Prompts

### Reference Updates
- adoption-approaches.md: Empirical data section
- reference.yaml: New deep_dive entries, updated line numbers

Sources: MetalBear engineering blog, arXiv studies, Addy Osmani (Jan 2026)

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

guide/workflows/plan-driven.md

@@ -244,6 +244,7 @@ Plans in `.claude/plans/` serve as decision documentation:
 
 ## See Also
 
+- [exploration-workflow.md](./exploration-workflow.md) — Explore alternatives before planning
 - [../ultimate-guide.md](../ultimate-guide.md) — Section 2.3 Plan Mode
 - [tdd-with-claude.md](./tdd-with-claude.md) — Combine with TDD
 - [spec-first.md](./spec-first.md) — Combine with Spec-First