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/workflows/task-management.md

@@ -220,6 +220,42 @@ Tasks survive:
 - System restarts
 - Multiple days of interruption
 
+#### ⚠️ Field Visibility Limitations
+
+**TaskList returns only**: `id`, `subject`, `status`, `owner`, `blockedBy`
+
+**Missing in TaskList output**:
+- `description` (requires TaskGet per task)
+- `metadata` (custom fields like priority, estimates)
+- `activeForm` (progress spinner text)
+
+**Workflow adjustment**:
+
+```bash
+# DON'T: Assume you can scan all descriptions
+TaskList  # Shows subjects only
+
+# DO: Fetch selectively
+TaskList                    # Get overview (which tasks exist, statuses)
+TaskGet(task-auth-login)    # Get full details for specific task
+TaskGet(task-auth-tests)    # Get details for next task
+```
+
+**When this matters**:
+- Complex projects with detailed task descriptions (>50 words per task)
+- Multi-agent coordination requiring shared context visibility
+- Need to quickly scan all task notes to decide resumption point
+
+**Cost awareness**:
+- TaskList = 1 API call
+- Fetching descriptions for N tasks = 1 + N calls
+- For 20 tasks, that's 20x overhead if you need all descriptions
+
+**Mitigation**:
+- Use `subject` field for critical info (visible in TaskList)
+- Keep `description` concise (50-100 words max)
+- Store detailed plans in markdown files (`docs/plan-*.md`)
+
 ### Resume Pattern
 
 ```bash