feat: pause campaign batches on SMTP failure

docs/CAMPAIGN_DELIVERY_RUNBOOK.md

@@ -62,6 +62,10 @@ Before the first live send for a sender domain or mail-server profile:
 6. If a synchronous request is used, keep Review and send open: it polls the
    durable counters while the request runs. A rejection occurs before SMTP and
    directs oversized runs to workers.
+7. Review the SMTP batch line. `ready` means DNS/connectivity/TLS/auth preflight
+   succeeded. Connection and reconnect counts explain reuse. `paused` means a
+   systemic transport failure stopped the remaining jobs before their SMTP
+   effect; test/correct the Mail profile and explicitly resume the queue.
 
 ## Outcome Handling
 
@@ -88,6 +92,9 @@ unknown provider attempt merely to repair the other layer's state.
 - `failed_temporary`: Retry explicitly after checking the error and retry count.
 - `failed_permanent`: Retry only if the operator has corrected the root cause and
   intentionally includes permanent failures.
+- `paused` after a systemic SMTP failure: do not resume until the shared Mail
+  profile passes its connection test. Authentication, sender rejection, and
+  unavailable connectivity affect the batch rather than one recipient.
 - `outcome_unknown`: Do not retry directly. Check SMTP logs, mailbox evidence, or
   provider control panels, then reconcile as accepted or not sent.
 - `claimed` or `sending` that does not progress: treat as a worker interruption.

docs/CAMPAIGN_HANDBOOK.md

@@ -611,7 +611,6 @@ The following are part of the selected reference journey but are not implied by
 the current baseline:
 
 - the final audited **test / single send / single resend** semantics;
-- reusable SMTP batch sessions and their measured throughput benefit;
 - durable, idempotent Campaign report delivery through a Mail-owned outbox
   ([`govoplan-mail#17`](https://git.add-ideas.de/GovOPlaN/govoplan-mail/issues/17));
 - a fully packaged one-command Campaign reference composition with production