fix(benchmark): encode URL state as UTF-8 before base64

[dumanoglu1]

Summary

• add UTF-8 safe encode/decode helpers for benchmark URL state
• use the helpers on both read and write paths instead of passing JSON directly to btoa/atob
• add a regression test covering non-Latin1 punctuation in persisted filter state

Fixes #65.

Testing

• npx vitest run app/benchmark/utils/useSearchParamsState.test.ts
• npm run typecheck
• npm run lint
• git diff --check

Note: local install reported existing npm audit findings and Node engine warnings because this machine runs Node 21.6.1 while the repo declares Node 24.x. Lint passed with existing img-element warnings outside the touched files.

[vercel]

@omerbek is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2