# Issues: add delete capability (soft + hard)

Child of musehub#141 (parent: framework-wide CRUD/delete idiom).

## Background

`MusehubIssue` (`musehub/db/musehub_social_models.py`) has no delete
concept at all — only `state` (`open`/`closed`). `close`/`reopen` are the
only lifecycle operations. There is no way to remove an issue, soft or
hard, via the CLI or API today. Confirmed hitting this directly during
#139's cleanup: ~40 test issues created for layout verification cannot be
removed, only closed.

## Goal

- Add an `is_deleted` column to `MusehubIssue`, matching the
  `MusehubIssueComment` pattern that already works.
- `muse hub issue delete <number>` — soft-deletes by default (sets
  `is_deleted`), matching #141's framework-wide idiom.
- `muse hub issue delete <number> --hard` — actually removes the row.
  Gate to repo owner/admin collaborator (same guard as other destructive
  issue operations).
- Soft-deleted issues excluded from `issue list` by default (add a
  `--include-deleted` flag for anyone who needs to see them), excluded
  from open/closed/unassigned counts on the issue list page.
- Decide and document: does a hard-deleted issue's number get reused, or
  stay permanently retired? (Recommend: retired — reusing numbers after
  hard-delete reintroduces exactly the kind of ambiguity #140 is about.)

## Out of scope

- Cascading behavior for comments/labels/anchors on a deleted issue —
  decide alongside the schema change, but keep simple: cascade delete on
  hard-delete, no special handling needed on soft-delete (comments stay,
  just orphaned from an invisible parent — same as GitHub's behavior).