The todo tool now supports hierarchical task lists: an item's optional
'parent' field points at another item's id, making it a subtask.
- tools/todo_tool.py: parent validated (self-ref dropped), dangling refs
and cycles sanitized; merge mode can set/clear parent; post-compression
injection renders the tree indented and keeps a finished parent visible
while any descendant is still active; the in-progress reorder pass is
skipped for nested lists (a flat move would tear subtasks from parents).
- Schema cost: ~45 tokens added to the cached tool schema (one string
property + one behavior sentence).
- acp_adapter/tools.py: todo result markdown indents by parent depth.
- Desktop: TodoItem carries parent; todoTree() DFS helper; composer
status stack renders subtask rows indented (depth-capped), stabilizer
compares depth.
- Docs: tools-reference todo entry mentions nesting.
Hydration/replay paths (gateway fresh-agent, API-server history) work
unchanged: parent rides inside the same todos array.
b6bd681e89