Fix HAL+JSON response detection

[mokevnin]

Summary

• extend JSON_CONTENT matcher to support structured syntax suffixes like application/hal+json
• add regression test for application/hal+json

Why

/api/v4/account can return application/hal+json. Current regex only allows application/json and application/vnd.*+json, so HAL responses are decoded as raw StringIO instead of JSON models.

Notes

• This is a minimal targeted fix in SDK runtime parsing.
• Full test run was not completed in local sandbox due to bundler cache write permissions; CI should validate the suite.