feat(notion-writer): add toggle blocks via HTML5 <details>

Multi-line <details>...</details> with optional <summary> emits a Notion
toggle block. Body recurses through _parse_lines so any block type
(lists, code, nested toggles) is supported inside. Depth tracking lets
<details> nest inside <details>. Unclosed <details> at EOF degrades to
plain paragraphs with a stderr warning instead of crashing.

+4 tests, 26 passing total.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/32-notion-writer/code/scripts/notion_writer.py

@@ -93,6 +93,49 @@ def _parse_lines(lines: List[str]) -> List[Dict[str, Any]]:
         if not line.strip():
             i += 1
             continue
+
+        # Toggle (HTML5 <details>) — multi-line form, depth-tracked for nesting
+        if line.strip() == '<details>':
+            i += 1
+            # Optional <summary>...</summary> on next non-blank line
+            summary_text = ''
+            while i < len(lines) and not lines[i].strip():
+                i += 1
+            if i < len(lines):
+                summary_match = re.match(r'^\s*<summary>(.*)</summary>\s*$', lines[i])
+                if summary_match:
+                    summary_text = summary_match.group(1)
+                    i += 1
+            # Collect body lines until matching </details>, depth-tracked
+            inner_lines: List[str] = []
+            depth = 1
+            while i < len(lines) and depth > 0:
+                stripped_inner = lines[i].strip()
+                if stripped_inner == '<details>':
+                    depth += 1
+                    inner_lines.append(lines[i])
+                elif stripped_inner == '</details>':
+                    depth -= 1
+                    if depth > 0:
+                        inner_lines.append(lines[i])
+                else:
+                    inner_lines.append(lines[i])
+                i += 1
+            if depth > 0:
+                # Unclosed <details> at EOF — degrade to paragraphs
+                import sys as _sys
+                print("Warning: unclosed <details> at EOF; emitting body as paragraphs",
+                      file=_sys.stderr)
+                if summary_text:
+                    blocks.append(create_paragraph_block(summary_text))
+                for inner in inner_lines:
+                    if inner.strip():
+                        blocks.append(create_paragraph_block(inner))
+                continue
+            children = _parse_lines(inner_lines)
+            blocks.append(create_toggle_block(summary_text, children))
+            continue
+
         if _is_table_row(line) and i + 1 < len(lines) and TABLE_SEPARATOR_RE.match(lines[i + 1]):
             header_cells = _split_table_row(line)
             i += 2
@@ -328,6 +371,18 @@ def create_callout_block(text: str, alert_type: str) -> Dict[str, Any]:
     }
 
 
+def create_toggle_block(summary_text: str, children_blocks: List[Dict[str, Any]]) -> Dict[str, Any]:
+    """Create a toggle block with summary rich-text and child blocks."""
+    return {
+        "object": "block",
+        "type": "toggle",
+        "toggle": {
+            "rich_text": parse_rich_text(summary_text),
+            "children": children_blocks,
+        },
+    }
+
+
 def create_code_block(code: str, language: str) -> Dict[str, Any]:
     return {
         "object": "block",

custom-skills/32-notion-writer/code/scripts/test_parser.py

@@ -211,6 +211,75 @@ def test_callout_unknown_falls_through():
     _assert("[!BOGUS]" in quote_text, "[!BOGUS] marker preserved in quote text")
 
 
+def test_toggle_basic():
+    md = "<details>\n<summary>Click to expand</summary>\n\nInner paragraph.\n</details>"
+    blocks = markdown_to_notion_blocks(md)
+    _assert(len(blocks) == 1, "one block emitted")
+    _assert(blocks[0]["type"] == "toggle", "block type is toggle")
+    summary_text = blocks[0]["toggle"]["rich_text"][0]["text"]["content"]
+    _assert(summary_text == "Click to expand", "summary text preserved")
+    children = blocks[0]["toggle"]["children"]
+    _assert(len(children) == 1, "one child block")
+    _assert(children[0]["type"] == "paragraph", "child is paragraph")
+
+
+def test_toggle_nested_blocks():
+    """Toggle body can hold any block type via _parse_lines recursion."""
+    md = """<details>
+<summary>Debug log</summary>
+
+- step one
+- step two
+
+```python
+print("hello")
+```
+</details>"""
+    blocks = markdown_to_notion_blocks(md)
+    _assert(blocks[0]["type"] == "toggle", "block is toggle")
+    children = blocks[0]["toggle"]["children"]
+    types = [c["type"] for c in children]
+    _assert("bulleted_list_item" in types, "list child preserved")
+    _assert("code" in types, "code child preserved")
+    code_block = next(c for c in children if c["type"] == "code")
+    _assert(code_block["code"]["language"] == "python", "code language preserved")
+
+
+def test_toggle_nested_toggle():
+    """details_depth tracking allows <details> inside <details>."""
+    md = """<details>
+<summary>outer</summary>
+
+<details>
+<summary>inner</summary>
+
+inner content
+</details>
+</details>"""
+    blocks = markdown_to_notion_blocks(md)
+    _assert(blocks[0]["type"] == "toggle", "outer block is toggle")
+    outer_children = blocks[0]["toggle"]["children"]
+    _assert(len(outer_children) == 1, "outer has exactly one child")
+    _assert(outer_children[0]["type"] == "toggle", "outer child is also toggle")
+    inner_summary = outer_children[0]["toggle"]["rich_text"][0]["text"]["content"]
+    _assert(inner_summary == "inner", "inner summary preserved")
+
+
+def test_toggle_unclosed_falls_through():
+    """Missing </details> at EOF degrades to paragraphs, no crash."""
+    md = "<details>\n<summary>oops</summary>\n\nbody line"
+    blocks = markdown_to_notion_blocks(md)
+    types = [b["type"] for b in blocks]
+    _assert("toggle" not in types, "no toggle emitted on unclosed <details>")
+    paragraph_texts = [
+        b["paragraph"]["rich_text"][0]["text"]["content"]
+        for b in blocks if b["type"] == "paragraph"
+    ]
+    joined = " ".join(paragraph_texts)
+    _assert("oops" in joined, "summary preserved as paragraph")
+    _assert("body line" in joined, "body preserved as paragraph")
+
+
 def test_rich_text_anchor_link_becomes_bold():
     """TOC-style fragment links must not be sent as Notion link annotations."""
     spans = parse_rich_text("see [Section A](#section-a) below")
@@ -266,6 +335,10 @@ def run_all():
         test_callout_warning,
         test_callout_caution,
         test_callout_unknown_falls_through,
+        test_toggle_basic,
+        test_toggle_nested_blocks,
+        test_toggle_nested_toggle,
+        test_toggle_unclosed_falls_through,
         test_rich_text_anchor_link_becomes_bold,
         test_rich_text_relative_link_becomes_plain,
         test_rich_text_absolute_link_preserved,