[Stability Testing: Test] Node Kill

[api-Hypernova]

Description: Add a test to the xmtp-qa-tools repo leveraging utilities from #836 that kills one xmtp-node container during active message traffic to confirm client reconnection and recovery.

Acceptance Criteria:

• Add a test executing the following steps:
• Spin up env
• Start message traffic
• Wait for steady state
• Kill one node container
• Validate message delivery, group consistency, retries, and client rejoin behavior
• Monitor log errors, retries, dropped messages, etc
• Stop message traffic
• Collect test artifacts
• Shutdown env