The original test only tested the _merge_emit_state helper in isolation
using mocks. Replace with integration tests that simulate the actual
state-tracking loop from _stream_events, including:
- Sequential emits with different keys preserve all keys (core bug)
- Proof that the bug manifests without current_graph_state.update
- Three sequential emits accumulate correctly
- Same key emitted twice uses latest value
- Non-dict emit does not corrupt current_graph_state
- Initial state reference is not mutated
Sequential emit_state calls with different keys now preserve all keys
in the snapshot. Previously, each call would replace the entire
manually_emitted_state, losing keys from earlier calls.
Jordan Ritter