fix(provider): include bankr and openai_responses in OpenAI-compatible failure classifier

[bukeeastrey]

Summary

Adds "bankr", "openai_responses", "volcengine_coding_plan", and "byteplus_coding_plan" to _OPENAI_COMPAT_PROVIDERS in failures.py so provider errors are correctly classified into actionable ProviderFailureKind states.

Problem

_OPENAI_COMPAT_PROVIDERS determines which providers use standard OpenAI HTTP error status classification. Because "bankr" and "openai_responses" were missing from this set:

• 401 / 403 errors were not mapped to ProviderFailureKind.AUTH_INVALID
• 402 errors were not mapped to ProviderFailureKind.INSUFFICIENT_CREDITS
• 404 / 400 errors were not mapped to ProviderFailureKind.MODEL_NOT_FOUND / BAD_REQUEST
• The runtime's decide_recovery_action() fell back to SURFACE rather than triggering doctor diagnostics, credential failures, or provider failover.

Changes Made

• Added "bankr", "openai_responses", "volcengine_coding_plan", and "byteplus_coding_plan" to _OPENAI_COMPAT_PROVIDERS in src/agentos/provider/failures.py.
• Extended the test parametrization in tests/test_provider_failure_classification.py to cover all newly registered providers across all failure status codes.

Verification

uv run pytest tests/test_provider_failure_classification.py tests/test_provider_failures.py -q
# 123 passed in 2.74s

uv run ruff check src/agentos/provider/failures.py tests/test_provider_failure_classification.py
# All checks passed!

uv run mypy src/agentos/provider/failures.py --show-error-codes
# Success: no issues found in 1 source file
closes #1126