feat(campaign): bound synchronous delivery

docs/CAMPAIGN_DELIVERY_RUNBOOK.md

@@ -5,10 +5,12 @@ been validated, built, reviewed, and locked.
 
 ## Operating Modes
 
-- Local direct send: `CELERY_ENABLED=false`. Queueing stores jobs in the DB, and
-  small development runs can be processed with "Send queued now".
+- Local direct send: `CELERY_ENABLED=false`. **Send now** is available only for
+  exact built runs within the effective synchronous limit. It preflights the
+  complete batch before the first SMTP effect.
 - Worker send: `CELERY_ENABLED=true` with Redis/Celery workers running. Queueing
-  publishes delivery tasks, and the Review & Send page polls summary counters.
+  publishes durable delivery tasks, and Review and send polls their persisted
+  summary counters even after the initiating request has returned.
 - Mock send: use only for development review. It does not prove real SMTP/IMAP
   credentials or server policy.
 
@@ -26,6 +28,8 @@ been validated, built, reviewed, and locked.
   ZIP before using production recipients.
 - Keep the report page open during tests; it is the operational source of truth
   for attempts, outcomes, and reconciliation.
+- Confirm the effective Send now recipient-job limit. The safe default is 25;
+  use Queue for workers for ordinary batches or any run above that limit.
 
 ## Deliverability Preflight
 
@@ -49,10 +53,15 @@ Before the first live send for a sender domain or mail-server profile:
 1. Validate the version with file checks enabled.
 2. Build the version and inspect all blocking review items.
 3. Queue only after the selected version is the intended immutable execution
-   version.
-4. In local mode, use "Send queued now" for small test runs.
+   version. Select **Queue for workers**, then verify the committed and
+   published counts.
+4. Use **Send now** only if the exact eligible count is non-zero and at or below
+   the effective deployment/tenant limit shown on the page.
 5. In worker mode, verify queue counters move from queued/claimed/sending to a
    terminal SMTP state.
+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.
 
 ## Outcome Handling