Fix flaky integration tests

[vrslev]

Fixes #160.

Changes:

• Wait for ActiveMQ Artemis to accept a STOMP CONNECT before running integration tests.
• Remove pytest reruns and the pytest-rerunfailures dependency so connection/startup failures are not masked.
• Make reconnect integration test deterministic by forcing reconnects instead of waiting on timing-based no-message restarts.
• Ensure the bulk integration producer waits until the subscription is registered.

Local verification:

• just lint
• just check-types
• just test-fast
• just test
• After cleanup: just install, just test-fast, targeted reconnect+bulk integration tests.

CI verification:

• 6 consecutive green CI runs total.
• 2 consecutive green CI runs after removing pytest-rerunfailures and destination mangling.