Implement two virtual node patterns for message flow orchestration:
- Sequence: Chains listeners in order (A→B→C), feeding each step's
output as input to the next. Uses ephemeral listeners to intercept
step results without modifying core pump behavior.
- Buffer: Fan-out to parallel worker threads with optional result
collection. Supports fire-and-forget mode (collect=False) for
non-blocking dispatch.
New files:
- sequence_registry.py / buffer_registry.py: State tracking
- sequence.py / buffer.py: Payloads and handlers
- test_sequence.py / test_buffer.py: 52 new tests
Pump additions:
- register_generic_listener(): Accept any payload type
- unregister_listener(): Cleanup ephemeral listeners
- Global singleton accessors for pump instance
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
