fix(datasets): apply validator to cached text before serving it

[devin-ai-integration]

TL;DR

fetchCachedTextFile now runs request.validate on cache hits too, so a malformed cached envelope is refetched and overwritten instead of poisoning every run.

What changed?

• src/datasets/cached-file.ts: cache hit is only returned when request.validate?.(cached.text) === undefined; otherwise fall through to download → validate → write (existing path).
• src/datasets/cached-file.test.ts: regression test seeding an HTML body under the cache key and asserting one origin request plus the envelope being replaced.

Why?

Follow-up to #79, which added validation before cache writes. Entries written before that (or by any other writer) still bypassed the validator on read, so a pinned cache with an HTML/rate-limit body would fail every benchmark run without ever refetching. Flagged by Devin Review on openrouter-web#41251.

How to test

bun test src/datasets/cached-file.test.ts

Expected: 19 pass, including "refetches and overwrites a cached entry the validator rejects".

Reviewer focus

• Requests without validate are unchanged (undefined?.(…) === undefined).

Checklist

• Tests cover changed behavior
• Public API or configuration changes are backward compatible, or the break is documented
• Benchmark changes document dataset provenance and licensing
• No credentials, private results, or restricted dataset contents are included
• Documentation is updated where needed

Link to Devin session: https://openrouter.devinenterprise.com/sessions/949ffdf48c7843febc66e0c2d8dc8486
Open in Devin Desktop: https://openrouter.devinenterprise.com/desktop/session/949ffdf48c7843febc66e0c2d8dc8486?variant=devin
Requested by: @abhinav-pola

[devin-ai-integration]

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---

Original prompt from Abhinav

SYSTEM:
<latest_message>
Abhinav Pola (U090K0G7JF3) [ts=1788974411.868429]: @Devinsync benchmark harness subtree
</latest_message>

=== BEGIN THREAD HISTORY (in #ecosystem-agents) ===
Abhinav Pola (U090K0G7JF3) [ts=1788974411.868429]: @Devinsync benchmark harness subtree
=== END THREAD HISTORY ===
Channel ID: C0BU53A7VEH
Thread URL: https://openrouter.slack.com/archives/C0BU53A7VEH/p1788974411868429?thread_ts=1788974411.868429&amp;cid=C0BU53A7VEH

The <latest_message> is the message that you should use to guide your goals + task for this session, and you should use the rest of the slack thread as context.
A [ts=...] marker on a Slack message is that message's timestamp. To act on a specific message with the slack tool (e.g. adding an emoji reaction via the reaction command), pass that value as timestamp along with the Channel ID — no extra lookup call is needed.