fix(state): deserialize display_metadata in get_messages and get_messages_around

[DavidMetcalfe]

What

get_messages() and get_messages_around() in hermes_state.py use SELECT * but don't deserialize the display_metadata column (added in #69771) from JSON. The frontend receives a raw JSON string, and the 'task_count' in message.display_metadata expression in chat-messages.ts throws TypeError because JavaScript's in operator requires an object, not a primitive.

How to reproduce

1. Have a session with an async_delegation_complete display event (any session that used delegate_task)
2. Resume it in Desktop or load messages via GET /api/sessions/{id}/messages
3. "Resume failed" popup with Cannot use 'in' operator to search for 'task_count' in {"delegation_id":...}

Fix

Add json.loads() for display_metadata in both get_messages() and get_messages_around(), matching the existing pattern for tool_calls and the pattern already in _rows_to_conversation().

Testing

• tests/test_hermes_state.py: 413 passed
• tests/hermes_cli/test_web_server.py -k session: 49 passed

Closes #70835

[isak-ialogics]

The fix covers both public retrieval paths, but the diff currently has no regression test exercising either one. Existing display_metadata coverage on current main only round-trips through conversation loading (get_conversation / _rows_to_conversation), which is why this omission could recur. Could you add a behavior test that stores non-empty metadata and asserts it is a dict with the original value from both get_messages() and get_messages_around()?

[DavidMetcalfe]

@isak-ialogics Thanks for the review! Added regression tests for both get_messages() and get_messages_around() — asserting that display_metadata is returned as a parsed dict (not a raw JSON string), plus a corrupt-JSON parse-failure test asserting the key is safely absent. All three fail pre-fix and pass with the deserialization in place.

Test suite: 416 passed (tests/test_hermes_state.py).

[teknium1]

Thanks for the focused report and regression tests.

Automated hermes-sweeper review found that current main already contains a broader implementation in 3399bf28a5ad268ad806378346f8be0e90cf3fdd (fix(state): decode display_metadata at every message read path):

• hermes_state.py:6158 decodes display_metadata in get_messages().
• hermes_state.py:6229 does the same in get_messages_around().
• hermes_state.py:5428 centralizes decoding, including invalid/non-object data and legacy double-encoded rows; it is also used by the conversation and anchored-view paths.
• tests/test_hermes_state.py:2751 covers all four read paths and malformed metadata.

The requested behavioral guarantee is therefore already implemented on main.