test(benchmark): use stable curl JSON fixture

[lntutor]

Summary

• replace the rotating https://mockhttp.org/json/1 benchmark input with the repository oc_pods.json fixture
• keep raw and RTK curl commands pointed at the same deterministic payload
• avoid false token-growth failures caused by two requests receiving unrelated JSON documents

Why

mockhttp.org/json/1 rotates among different response bodies. The benchmark performs separate raw and RTK requests, so it can compare different documents and report apparent token growth even when RTK behavior is unchanged. This is reproducible on develop.

Using a local file URL makes the comparison deterministic and requires no runtime code changes.

Validation

• bash -n scripts/benchmark.sh
• git diff --check
• release build
• curl benchmark row: 2523 -> 2523 (+0%)