Epic & sub-issue projection

[androidand]

Epic & sub-issue projection

Why

Larger efforts span multiple repos and phases. A common pattern is one "epic"
issue that coordinates several sub-issues, where each sub-issue is the unit that
gets a branch, a worktree, and — once implementation starts — a focused spec.
specsync should understand this hierarchy so an epic stays a coordination shell
while each sub-issue maps one-to-one to an OpenSpec change.

What

• Recognize an epic by a convention (a label/marker such as type:epic), not by
  having a spec of its own — an epic is a list/coordination issue.
• Map each sub-issue to one OpenSpec change (one change ⇄ one sub-issue).
• Keep the epic's body in sync with the set of sub-issues (checklist or links),
  while each sub-issue's body is driven by its change's proposal + tasks.

Scope

• Epic detection convention + a parent link on a change.
• Sub-issue projection: child change ⇄ sub-issue.
• Epic body roll-up of its sub-issues.

Tasks

Tasks: Epic & sub-issue projection

• Define the epic convention (type:epic marker/label) and a parent link field
• Project a child change to a sub-issue under its epic
• Roll up sub-issue references into the epic body
• Do not require or create a spec for the epic itself