What does this PR do?

Fixes `#15218`. `run_conversation` was calling `memory_manager.sync_all(original_user_message, final_response)` at the end of every turn where both args were present, without considering the `interrupted` local flag. Result: an external memory backend received partial assistant output, aborted tool chains, or mid-stream resets as durable conversational truth — downstream recall then treated the not-yet-real state as if the user had seen it complete, poisoning the trust boundary between "what the user took away from the turn" and "what Hermes was in the middle of producing when the interrupt hit".

Reporter's minimal-fix suggestion was to gate on `not was_interrupted`; I implemented that with a small refactor that also makes the logic testable in isolation.

Fix

Extracted the inline sync block in `run_conversation` into a new private method on `AIAgent`:

```python
def _sync_external_memory_for_turn(
self,
*,
original_user_message: Any,
final_response: Any,
interrupted: bool,
) -> None:
if interrupted:
return
if not (self._memory_manager and final_response and original_user_message):
return
try:
self._memory_manager.sync_all(original_user_message, final_response)
self._memory_manager.queue_prefetch_all(original_user_message)
except Exception:
pass
```

Why a helper instead of a one-line guard at the call site?

• The interrupt guard becomes a single visible check at the top of the method instead of hidden in a boolean-and at the call site
• Gives tests a clean seam to assert on — the pre-fix layout buried the logic inside the 3,000-line `run_conversation` function where no focused test could reach it
• Zero behavior change for the positive path
• The prefetch side-effect is also gated on the same interrupt flag — the user's next message is almost certainly a retry of the same intent, and a prefetch keyed on the interrupted turn would fire against stale context

Skip conditions, encoded explicitly

Related Issue

Fixes #15218

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ♻️ Refactor (no behavior change) — extracted inline sync block into a helper
• ✅ Tests (adding or improving test coverage)

Test plan

• 16 new tests in `tests/run_agent/test_memory_sync_interrupted.py` — all green on py3.11 venv
• Existing `test_memory_provider_init.py` still green — the refactor preserves the positive path exactly
• Import smoke check on `run_agent` module
• No pre-existing tests assert on `memory_manager.sync_all` — grep -rn confirmed the seam is new

Test coverage detail

`TestSyncExternalMemoryForTurn` (16 tests):

• `test_interrupted_turn_does_not_sync` — core fix
• `test_interrupted_turn_skips_even_when_response_is_full` — a long seemingly-complete response is still partial if `interrupted=True`; the strings-on-disk lie
• `test_completed_turn_syncs_and_queues_prefetch` — regression guard for the positive path; `sync_all` AND `queue_prefetch_all` both called with the right args
• `test_no_final_response_skips` / `test_no_original_user_message_skips` / `test_no_memory_manager_is_a_no_op` — pre-fix skip paths preserved
• `test_sync_exception_is_swallowed` / `test_prefetch_exception_is_swallowed` — best-effort invariant
• `test_sync_matrix` — 8-case parametrised matrix over (interrupted × final_response × user_message), asserts sync fires iff `interrupted=False` AND both strings are non-empty

Not in scope

• Exposing a structured turn-status to memory providers so they can make their own skip decisions — the reporter mentioned this as an alternative; bigger API surface, saving it for a follow-up if maintainers want it
• Add write-origin metadata for external memory provider writes #15219 (write-origin metadata for memory writes) — same neighbourhood, separate change; the reporter filed both at once