Transient item_store failures return an opaque error without details or request ID #373

Observed 2026-10-03 by Claude Code: during a window of roughly 15-20 minutes, item_store failed 6 times with only 'An error occurred invoking item_store' (no code, detail or request ID). Five failures were creates with ~400-1900-character content, one an update with long content. Short creates and some updates succeeded in the same window.

Follow-up: shortly afterwards the exact payload that had failed (the ~1300-character multi-line room audit) succeeded unchanged in project tmp (probe tasks #24-#26, archived). So the failures were most likely transient and server-side, not caused by the content.

Remaining issue: the error gives no hint whether to retry or fix the input. Suggest returning structured errors (transient vs validation), a request or correlation ID, and logging server exceptions so incidents like this can be traced.