Sub-issues under a parent can be grouped into ordered stages (issue.stage).
The child-done -> parent notification + assignee wake now fire only when a
stage barrier closes: every sub-issue in the lowest unfinished stage has
reached a terminal status (done/cancelled). An unstaged sibling set is one
implicit stage, so the parent is woken once when the last sub-issue finishes
instead of on every child — the default fix for the fire-on-every-child
cascade reported in discussion #4320 / MUL-3508.
Stage advancement stays agent-driven: the server only detects the closed
barrier and wakes the parent assignee, who decides whether to promote the
next stage.
- DB: nullable issue.stage (CHECK >= 1) + sqlc regen
- API: stage on issue create/update/response and batch update
- CLI: `issue create`/`issue update` --stage; new `issue children` command
that lists sub-issues grouped by stage (table + json)
- stageBarrierClosed / stageProgressSummary in issue_child_done.go, with the
wake comment now stage-aware, plus unit tests
- skill docs (multica-working-on-issues SKILL.md + source map)
Web UI (create-form stage picker, sidebar edit, group-by-stage display) is a
follow-up; the API already returns stage for it to consume.
MUL-3508
Co-authored-by: multica-agent <github@multica.ai>
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