`dsh-tool-todo-tree`: A Mutually Exclusive Alternative to DSH's Tree-Structured `todo_write`

dsh-tool-todo-tree is a tree-structured task management plugin for DeepSeek Harness (DSH), serving as a mutually exclusive alternative to the flat-list tool dsh-tool-todo. It modifies the data structure of the todo_write tool to support a parent-child hierarchical task tree, nesting nodes via the `children` field, and provides a depth-indented plan bar display on the web interface. This plugin supports full replacement writes of the task tree and replays event snapshots using a last-write-wins strategy. Core features include: support for the `allowParallelInProgress` configuration to control parallel progress states; enforcement that parent nodes can only be marked as completed after all child nodes are finished; and automatic deduplication of sibling node content at the same level with normalization of empty child nodes.