feat: add plan review loop and checkbox syntax to writing-plans skill

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

skills/writing-plans/SKILL.md

@@ -48,14 +48,14 @@ 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`
 - Modify: `exact/path/to/existing.py:123-145`
 - Test: `tests/exact/path/to/test.py`
 
-**Step 1: Write the failing test**
+- [ ] **Step 1: Write the failing test**
 
 ```python
 def test_specific_behavior():
@@ -63,24 +63,24 @@ def test_specific_behavior():
     assert result == expected
 ```
 
-**Step 2: Run test to verify it fails**
+- [ ] **Step 2: Run test to verify it fails**
 
 Run: `pytest tests/path/test.py::test_name -v`
 Expected: FAIL with "function not defined"
 
-**Step 3: Write minimal implementation**
+- [ ] **Step 3: Write minimal implementation**
 
 ```python
 def function(input):
     return expected
 ```
 
-**Step 4: Run test to verify it passes**
+- [ ] **Step 4: Run test to verify it passes**
 
 Run: `pytest tests/path/test.py::test_name -v`
 Expected: PASS
 
-**Step 5: Commit**
+- [ ] **Step 5: Commit**
 
 ```bash
 git add tests/path/test.py src/path/file.py
@@ -95,6 +95,25 @@ git commit -m "feat: add specific feature"
 - Reference relevant skills with @ syntax
 - DRY, YAGNI, TDD, frequent commits
 
+## Plan Review Loop
+
+After completing each chunk of the plan:
+
+1. Dispatch plan-document-reviewer subagent (see plan-document-reviewer-prompt.md) for the current chunk
+   - Provide: chunk content, path to spec document
+2. If ❌ Issues Found:
+   - Fix the issues in the chunk
+   - Re-dispatch reviewer for that chunk
+   - Repeat until ✅ Approved
+3. If ✅ Approved: proceed to next chunk (or execution handoff if last chunk)
+
+**Chunk boundaries:** Use `## Chunk N: <name>` headings to delimit chunks. Each chunk should be ≤1000 lines and logically self-contained.
+
+**Review loop guidance:**
+- Same agent that wrote the plan fixes it (preserves context)
+- If loop exceeds 5 iterations, surface to human for guidance
+- Reviewers are advisory - explain disagreements if you believe feedback is incorrect
+
 ## Execution Handoff
 
 After saving the plan: