fix(client): cap Retry-After at 60s

[redactdeveloper]

Summary

• restore the 60s cap for Retry-After / retry-after-ms delays
• fall back to the normal exponential backoff when the server asks for an unreasonable wait
• add regression coverage for a 600s Retry-After response

Tests

• ./scripts/test tests/index.test.ts
• ./node_modules/.bin/prettier --check src/client.ts tests/index.test.ts
• ./node_modules/.bin/tsc --noEmit --skipLibCheck --target es2020 --lib es2020,dom,dom.iterable --module commonjs --moduleResolution node --esModuleInterop --strict --exactOptionalPropertyTypes --noUncheckedIndexedAccess --noImplicitOverride --noPropertyAccessFromIndexSignature src/client.ts

Fixes #1840