fix: remove checkbox from task headings, keep on steps only

The `- [ ] ### Task N:` syntax was unusual and might not render
correctly in all markdown parsers. Now only steps have checkboxes.

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

skills/writing-plans/SKILL.md

@@ -34,7 +34,7 @@ Assume they are a skilled developer, but know almost nothing about our toolset o
 ```markdown
 # [Feature Name] Implementation Plan
 
-> **For Claude:** REQUIRED: Use superpowers:subagent-driven-development (if subagents available) or superpowers:executing-plans to implement this plan. Tasks and steps use checkbox (`- [ ]`) syntax for tracking.
+> **For Claude:** REQUIRED: Use superpowers:subagent-driven-development (if subagents available) or superpowers:executing-plans to implement this plan. Steps use checkbox (`- [ ]`) syntax for tracking.
 
 **Goal:** [One sentence describing what this builds]
 
@@ -48,7 +48,7 @@ Assume they are a skilled developer, but know almost nothing about our toolset o
 ## Task Structure
 
 ````markdown
-- [ ] ### Task N: [Component Name]
+### Task N: [Component Name]
 
 **Files:**
 - Create: `exact/path/to/file.py`

skills/writing-plans/plan-document-reviewer-prompt.md

@@ -22,7 +22,7 @@ Task tool (general-purpose):
     | Completeness | TODOs, placeholders, incomplete tasks, missing steps |
     | Spec Alignment | Chunk covers relevant spec requirements, no scope creep |
     | Task Decomposition | Tasks atomic, clear boundaries, steps actionable |
-    | Task Syntax | Checkbox syntax (`- [ ]`) on tasks and steps |
+    | Task Syntax | Checkbox syntax (`- [ ]`) on steps for tracking |
     | Chunk Size | Each chunk under 1000 lines |
 
     ## CRITICAL