#43 issue edit: --milestone/--label/--assignee flags (gh-literal)

SOURCE: wr1te swarm #1+#4 (verified on current main): f0rge issue edit <id> accepts ONLY --title/--body; milestone/label/assignee flags advertised in the shared flags line but rejected; post-hoc milestone grouping requires hand-editing .forge/issues/<uuid>/ issue.md. gh-literal: gh issue edit accepts --milestone --label --assignee. FIX: f0rge issue edit <id> [--title T] [--body B] [--milestone M] [--label L] [--assignee A] — each optional; --label/--assignee follow the existing label/assign verbs' semantics (replace or append consistently); --state stays REJECTED (close/reopen = gh path) and the shared flags line stops advertising --state for edit. DONE: edit --milestone groups an existing issue; edit --state exit 2 with try-path; help truthful.