fix(streaming): derive correct status code from SSE error type instead of HTTP 200

[tao-to-python]

Description

Fixes incorrect error classification for mid-stream SSE errors, as reported in #1258.

Problem

When the API starts streaming (HTTP 200) then sends an SSE error event like overloaded_error, the SDK creates an APIStatusError with status_code=200 because _make_status_error dispatches on self.response.status_code.

This means:

• OverloadedError (529) is never raised for mid-stream overload errors
• RateLimitError (429) is never raised for mid-stream rate limits
• Retry logic that catches specific error types doesn't work

Solution

Add an _SSE_ERROR_TYPE_TO_STATUS mapping that derives the correct HTTP status code from the error body type:

_SSE_ERROR_TYPE_TO_STATUS = {
    "overloaded_error": 529,
    "rate_limit_error": 429,
    "invalid_request_error": 400,
    ...
}

When a mapped error type is found, create a synthetic httpx.Response with the correct status code so _make_status_error returns the right error subclass.

Changes

File	Change
src/anthropic/_streaming.py	Add error type → status code mapping for sync + async paths

Fixes #1258