Exclude the current attempt from prior-attempt runtime guards

When dispatch persists an attempt before handing it to a worker, a repeated runtime guard must distinguish that current attempt from earlier attempts. Otherwise a duplicate-prevention query can discover the row created moments earlier and block the operation itself. Pass the current provider identity into the runtime history check and exclude exactly that identity from the prior-attempt predicate. Keep dispatch preflight and every genuinely earlier attempt visible. Test current-only, prior-plus-current and another-resource histories separately. This fixes self-blocking; it does not provide atomic admission against simultaneous dispatches or justify weakening duplicate prevention.

Applies when: A worker repeats a history-based admission check after its attempt has already been persisted. Keywords: current attempt history duplicate guard dispatch worker self blocking identity