Integration test hangs on second node subscription (Bob) after Subscribe fix

[sanity]

Problem Description

After implementing the Subscribe fix in freenet-core PR #1844, the River integration test now progresses further but still hangs on the second node's (Bob's) subscription attempt. Alice's subscription now works correctly, indicating the initial Subscribe issue has been resolved, but there appears to be an issue with multiple/concurrent subscriptions.

Reference Issues

• Original issue: WebSocket Subscribe Response Not Received in River Integration Tests #33
• Related freenet-core fix: Fix: WebSocket SubscribeResponse not being delivered to clients freenet-core#1844

Current Behavior

1. Alice's subscription to the room now works correctly ✅
2. Test progresses beyond the initial Subscribe hang
3. Test hangs when Bob (second node) attempts to subscribe to the same room ❌

Test Location

The test hangs in the integration test, specifically when the second node tries to subscribe after the first node has successfully subscribed.

Environment Requirements

• CARGO_TARGET_DIR must be set for contract compilation to work properly
• Freenet version: Latest with Subscribe fix from PR #1844
• Test: River integration test

Expected Behavior

Both Alice and Bob should be able to subscribe to the same room without the test hanging.

Hypothesis

This suggests there may be an issue with:

• Multiple nodes subscribing to the same contract/room
• Concurrent subscription handling in the Freenet network
• State synchronization between subscribed nodes
• Contract state management with multiple subscribers

Next Steps

1. Investigate how Freenet handles multiple subscriptions to the same contract
2. Check if there are race conditions in the subscription process
3. Verify contract state updates are properly propagated to all subscribers
4. Test with sequential vs concurrent subscriptions

[AI-assisted debugging and comment]

[sanity]

Closing as the root cause is addressed in freenet/freenet-core#1848. The multi-node subscription failures are symptoms of the subscription topology problems being fixed there. [AI-assisted debugging and comment]