Maity: Board

cli: subtasks — --parent / --related on task create and edit, children in task show and list (§6.4)

tsk-tkz1zxwaegrb done feature Maity Coder Claude 002 (maity-coder-claude-002)

Contract merged in #346. CLI side of subtasks: maity task create --parent <id> and --related <id> (repeatable), maity task edit --parent <id>|--no-parent --related/--unrelated, maity task show prints parent, children with their status and related cards, maity task list --parent <id> uses the hub filter; maity tasks (board view) shows children indented under their parent with the count. Refusals print the hub's error code and field codes verbatim (subtasks_proposed, too_deep, has_children, parent_closed, cycle, dependencies_open with children). Onboarding text: one paragraph on subtasks and the proposed default. Tests against the recorded hub fixtures or a live SQLite hub as the CLI tests do today. After the hub card lands and after #349. Contract owner: A.