docs: plan managed EventPrompt test identity

Problem: the payload singleton test used identical managed and impostor content, so it could not prove which item survived.\n\nRisk: both test strings must still satisfy the conservative generated signature.

docs/plans/todo-53.4-managed-event-prompt-test-identity.md

@@ -0,0 +1,20 @@
+# Todo 53.4: Managed EventPrompt Test Identity
+
+## Problem
+
+The Todo 53.3 behavior test gives the managed EventPrompt and generated-signature custom impostor identical content. Its expected output therefore proves only that one string remains, not that the collector retained the managed item.
+
+## Scope
+
+- Change only `tests/test_websocket_api.py`.
+- Use two different strings that both satisfy the conservative generated EventPrompt signature.
+- Assign one to the custom impostor and the other to the managed `event_agent_system` item.
+- Assert `dual_agent` retains the managed content and rejects the impostor.
+- Assert `chat_agent_tools` rejects both generated contents while preserving ordinary custom prompts.
+- Do not change production code.
+
+## Verification
+
+- Run the focused EventPrompt test and the full WebSocket test file.
+- Run Node syntax and diff checks.
+- Repeat specification and code-quality review for Todo 53.3/53.4 together.

docs/plans/todos.md

@@ -118,3 +118,4 @@
 | 53.1 | done | `docs/plans/todo-53.1-event-prompt-order-preservation.md` | Preserve the user-selected EventPrompt position while mode/tool refreshes still deduplicate and regenerate its content. | RED: `3 failed, 5 passed`; GREEN: focused `8 passed`, full WebSocket file `84 passed`; Node syntax and diff checks pass; behavior tests cover refresh, mode round trip, restore position, and duplicate cleanup. |
 | 53.2 | done | `docs/plans/todo-53.2-console-interaction-state.md` | Make the new collapsible control sections and Audit/Usage drawer operable, persistent, and synchronized with session/mode status. | RED: `6 failed, 9 passed`; GREEN: focused `15 passed`, full WebSocket file `94 passed`; Node/diff checks and independent spec/code-quality reviews pass. |
 | 53.3 | in_progress | `docs/plans/todo-53.3-event-prompt-payload-singleton.md` | Enforce the EventPrompt singleton at the outbound payload boundary in both invocation modes, including stale or user-edited generated-signature custom prompts. | A failing behavior test proves `dual_agent` sends one managed EventPrompt and `chat_agent_tools` sends none; focused/full tests and review gates pass. |
+| 53.4 | in_progress | `docs/plans/todo-53.4-managed-event-prompt-test-identity.md` | Make the payload-singleton regression distinguish the managed EventPrompt from a generated-signature custom impostor. | The test uses different valid generated-signature contents and proves dual mode retains the managed value while direct mode retains neither. |