Indirect timeout in Cait-Sith

[SimonRastikian]

Background

The distinct_reconstruction_thresholds tests inferred the Cait-Sith timeout indirectly by racing it against a metric counter.

User Story

No response

Acceptance Criteria

• The replace the metric race in the distinct-reconstruction-thresholds test with a direct assertion on the sign request's on-chain timeout failure.

Resources & Additional Notes

Original comment by @kevindeforth: #3640 (comment)
PR by @SimonRastikian: #4051
Followup discussion suggesting closing PR 4051: https://nearone.slack.com/archives/C0912BTG51T/p1787564203519989?thread_ts=1785860204.395819&cid=C0912BTG51T