fix: decode JWT claims as UTF-8

[nicknisi]

Fix workos/authkit-js issue #144 (#144): getClaims / decodeJwt in src/utils/jwt.ts garble non-ASCII claim values. decodeBase64Url returns atob(...), which yields one character per byte, and the result goes straight to JSON.parse, so a claim like Acme Café comes out as Acme Café. Decode the bytes as UTF-8 before parsing, for both the header and the payload. The issue suggests new TextDecoder().decode(Uint8Array.from(binary, c => c.charCodeAt(0))). Add regression tests in src/utils/jwt.test.ts: a payload with a multi-byte claim (Acme Café), plus a claim using a 4-byte character such as an emoji, round-tripped through decodeJwt and getClaims. Each test must fail on the old code and pass on the new. Plain-ASCII behaviour and error handling must stay unchanged.

Riker's check npx jest src/utils/jwt.test.ts && npm run format:check && npm run build passed.

Opened as a draft by Riker (job 119).

[greptile-apps]

Confidence Score: 5/5

[Critical impact] This PR appears safe to merge.

Summary

Fixes garbled non-ASCII JWT values by decoding header and payload bytes as UTF-8 before parsing.

• JWT headers and claims now keep their UTF-8 text.

_{Reviews (1) · Last reviewed commit: "fix: decode JWT claims as UTF-8" · Reviewed by Greptile}