cell_pm_complete, main_pm_complete, and submit_up already had subtask-
terminality gates inherited from the pre-gateway closure check at
roboco/services/task.py. This commit verifies the gate is preserved
and improves the remediation hint to actually NAME the non-terminal
subtasks instead of telling the PM to "call triage()".
The improvement uses a new private helper
``Choreographer._non_terminal_subtask_ids`` that queries get_subtasks
and filters to non-terminal statuses, returning a comma-separated
list of "<id> (<status>)" pairs. The PM now sees exactly which
subtasks are blocking the parent's completion.
Pre-gateway reference: roboco/services/task.py closure check
(documented in PRE_GATEWAY_LIFECYCLE.md §4.3).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
