[PATCH] Remove #:streaming? #t from HTTP requests to fix JSON parsing

[jgart <jgart@dismail.de>]

Hi Arun,

I ran into a bug where json-request would throw a JSON-invalid
exception when talking to OpenAI-compatible APIs. The issue is that
#:streaming? #t in http-request bypasses Guile's automatic
content-encoding decompression (gzip) and chunked transfer decoding.
So json->scm was receiving raw gzip-compressed bytes instead of the
actual JSON text.

The fix is straightforward:
- Drop #:streaming? #t so http-request returns a clean, fully-decoded
  bytevector.
- Switch from json->scm (port-based) to json-string->scm (string-based),
  decoding the bytevector with utf8->string.
- Remove the set-port-encoding! call since we no longer work with a
  port.

I also noticed that openai-models was working around this with an
accept-encoding: identity header. That workaround is no longer needed
once Guile handles decompression normally?

Thanks,

jgart