Deleting a profile-backed runtime instance is refused while its profile exists,
and the refusal said "delete its runtime profile instead". For the case that
produces it most often — a retired machine's leftover row in a profile other,
healthy machines still use — that points at a workspace-wide delete which takes
those machines' runtimes too, and which a bound agent refuses anyway with a
second message naming no agent and no machine.
Retention GC already deletes these rows after 7 days offline, ignoring
profile_id, so the refusals now describe that instead of recommending the
destructive route:
- Instance refusal is status-aware, and only promises automatic cleanup when it
matches the gate gcRuntime actually applies: the runtime's own undrained
tasks plus those owned by every user agent bound to it, archived included.
- Profile refusal names the blocking agents and the machine each sits on, with
a per-class remedy — ordinary agents can be reassigned or archived; Mika
cannot be archived but can be rebound; a Builder session is reachable only by
its creator. Those clauses come from counts over the whole blocker set, so a
class outside the 20-row sample is still reported.
- Response bounded at 20 entries with an exact total, capping rows read inside
the locked delete transaction.
- CLI surfaces the server's sentence instead of dumping the raw JSON body.
When a delete is allowed or refused is unchanged; the guard predicates and the
instance-refusal error code are untouched. The remaining capability gap —
retiring an offline instance on demand — is tracked separately.
Fixes MUL-7409
