fix: dispatch AMQP acknowledgements to the owning connection

[robjarawan]

Closes #145.

I changed Gather.ack() to check the existing connection_id before handing an AMQP acknowledgement to a consumer. Previously, the first consumer on the same broker erased the second consumer's ack_id, so the owning connection never acknowledged that delivery.

I reproduced this with a disposable RabbitMQ 4.3.5, parsed subscriptions, real gather/acknowledgement calls and a queue check after closing the consumers. Both amqp and amqpconsumer redelivered subscription 1's message on the baseline. With the fix, neither backend redelivers either message. The single-subscription controls pass before and after.

Check	Baseline	Fix
Local RabbitMQ, two subscriptions per backend	Second delivery returned on both backends	No redelivery
Local RabbitMQ, one subscription per backend	Pass	Pass
Transport-isolated regressions and recovery controls	4 failed, 7 passed	11 passed
Broader unit suite, excluding Azure's external-emulator tests	See existing baseline evidence	364 passed, 1 skipped, 1 failed

The remaining broader failure is the existing clock-dependent test_schedules. I kept the stale-connection, changed-channel and transport-error controls so the fix preserves the recovery behavior from upstream #1155 and #1278. No ACK retry loop or reconnect was added. Protocols without connection_id keep their existing dispatch behavior.

python -m pytest -q tests/sarracenia/flowcb/gather/ack_owner_test.py

For the real-broker reproduction, start a disposable RabbitMQ on loopback with the standard local guest fixture account, then run:

python tests/sarracenia/flowcb/gather/ack_owner_broker.py

The script creates uniquely named queues/exchanges, publishes synthetic messages, reports actual redeliveries and removes only its own resources. The same script exits 1 on the baseline and 0 with the fix.

The runtime fix and tests are in 11ac81734. I carried the separate CI repair from #140 for local maintenance fixtures and exclusion of live-feed dynamic_flow jobs. This remains a draft pending the broader flow matrix and independent review.

[github-actions]

Test Results

385 tests   384 ✅  1m 42s ⏱️
  1 suites    1 💤
  1 files      0 ❌

Results for commit 24141ec.