fix(client): normalize headers and response handling for local /request

[Miskler]

Problem

The TLS client implementation was brittle in multiple places:

• Response body: server sometimes returned bytearray(...), HTML error pages, or gzip-encoded data → JSON decoding failed with orjson.JSONDecodeError.

• Response headers: geventhttpclient exposed headers as generators or bytes, not as a clean dict, causing .items() errors and type mismatches.

• Request headers: outgoing headers mixed str and bytes or contained non-string values (int), leading to

  • TypeError: can't concat str to bytes in geventhttpclient;
  • BrowserContext.set_extra_http_headers: expected string, got number when rendering with Playwright.

When it happens

• Whenever the local Go server returns non-JSON payloads (HTML errors, bytearray(...) wrappers, gzip).
• When headers are not normalized (generator, bytes, or numeric values).
• When sending requests to /request without a proper Content-Type: application/json.
• During .render(), if any header value is not a string (e.g. X-City: 229 as an integer).

Solution

• Added _normalize_headers to coerce any header format (generator, bytes, tuples) into dict[str,str|list[str]].

• Introduced _SanitizedCID, a CaseInsensitiveDict subclass, that forces all header values to str on insert/update.

• Outgoing requests to /request now always use geventhttpclient.header.Headers with Content-Type: application/json and Accept: application/json.

• Response body is read once and normalized:

  • decompress via Content-Encoding: gzip;
  • unwrap bytearray(...) repr if present;
  • explicit error if server returns HTML/non-JSON.

• Minor fixes: safe handling of timeoutMilliseconds, insecureSkipVerify, and base64 only for true byte bodies.

• Improved error messages with safe body prefixes for diagnostics.

Result

• Stable JSON parsing regardless of how the local server formats its response.
• No more type errors from header handling in geventhttpclient or Playwright.
• Clearer, actionable error messages when the server responds with invalid payloads.