Add an integration reproducer for attachment update 4999 failures

[Flerpharos]

Summary
Add a reproducible integration path for attachment update requests that return LabArchives 4999.

Scope

• capture the minimal failing update flow
• record the request shape and metadata needed to reproduce the failure
• isolate the reproducer as opt-in integration coverage or a documented scripted workflow

Acceptance criteria

• maintainers can rerun a documented reproducer
• the failure mode is captured with enough detail to compare fixes
• the reproducer does not run unintentionally in the unit test suite