docs: document Tasks API field visibility limitations (Gang Rui analysis)

Integration of community practitioner feedback on Tasks API (v2.1.16+)
field visibility constraints discovered through real-world usage.

Changes:
- guide/ultimate-guide.md:
  * Added 3 rows to comparison table (field visibility, metadata, overhead)
  * New subsection "⚠️ Tasks API Limitations (Critical)" (~40 lines)
  * Field visibility constraint table, cost examples, 3 workaround patterns

- guide/workflows/task-management.md:
  * New subsection "⚠️ Field Visibility Limitations" (~35 lines)
  * Workflow adjustments, cost awareness, mitigation strategies

- guide/cheatsheet.md:
  * Added limitation note with actionable tip (~3 lines)

- machine-readable/reference.yaml:
  * 4 new entries: limitations, field_visibility, cost_overhead, workarounds
  * Updated resource_evaluations_count: 16 → 22

- docs/resource-evaluations/016-gang-rui-tasks-api-limitations.md:
  * New comprehensive evaluation (score 5/5 CRITICAL)
  * Fact-check, challenge phase, integration details

- README.md:
  * Updated resource evaluations count: 15 → 22 assessments

Score: 5/5 (CRITICAL) - Breaks recommended workflow, 11x-51x cost
overhead, prevents user frustration, maintains guide credibility.

Source: https://www.linkedin.com/posts/limgangrui_i-explored-the-new-claude-codes-task-system-activity-7420651412881268736-Hpd6
Date: 2026-01-24

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

guide/cheatsheet.md

@@ -396,6 +396,11 @@ claude
 - 🔄 **Multi-session**: Broadcast state to multiple terminals
 - 📊 **Status**: pending → in_progress → completed/failed
 
+**⚠️ Limitation**: TaskList shows `id`, `subject`, `status`, `blockedBy` only.
+For `description`/`metadata` → use `TaskGet(taskId)` per task.
+
+**Tip**: Store key info in `subject` for quick scanning.
+
 **Migration flag** (v2.1.19+):
 ```bash
 # Revert to old TodoWrite system