Stream error payloads crash when code is non-numeric

[saxon134]

error_from_stream_payload() converts error.get("code") with int(...). The rest of the SDK treats error.code as a string code, and stream error frames can carry symbolic codes; in that case iter_sse_models()/aiter_sse_models() raise ValueError instead of GlobalRouterError. A minimal reproducer is an SSE frame like data: {"error":{"code":"rate_limit_error","message":"limited"}}, which reaches this line and fails during int conversion.

File: src/globalrouter/_errors.py

Line: 69

Severity: medium

Summary: int cast of stream error code

[saxon134]

Coding Loop Plan

Refined Issue

Stream error payloads currently call int(error.get("code") or 0), so SSE error frames with a non-numeric error.code raise ValueError instead of GlobalRouterError.

Implementation Plan

Add a regression test for SSE stream error payloads whose error.code is non-numeric, then update stream error normalization to parse status_code defensively. Keep the change scoped to stream error payload handling and preserve existing HTTP error normalization behavior.

Development Tasks

1. Handle non-numeric stream error codes safely
   In src/globalrouter/_errors.py, update error_from_stream_payload so error.code is never passed directly to int() without validation. Convert numeric int-like values to status_code, and fall back to 0 for missing or non-numeric values. Also normalize GlobalRouterError.code from metadata.router_code when present, otherwise from error.code when it is present, otherwise GLOBALROUTER_STREAM_ERROR. Add a focused regression test in tests/test_client.py that feeds an SSE error frame with error.code set to a non-numeric string and asserts a GlobalRouterError is raised rather than ValueError, with status_code == 0 and code reflecting the stream error code or router_code normalization.
   Files: src/globalrouter/_errors.py, tests/test_client.py
   Tests: pytest tests/test_client.py -q