Previously, only timeout and network errors (matched via string
patterns) were retried. HTTP 500 server errors from
OpenRouter/OpenAI-compatible providers would fail the agent turn
immediately when no model fallback candidate was available.
This commit replaces the separate timeout/network retry branches
with a unified transientLLMRetryReason() helper that:
1. Uses providers.ClassifyError() to detect server_error (HTTP >=500),
timeout, network, and rate_limit errors
2. Falls back to the existing string-based detection for errors
not classified by the provider
A regression test (TestPipeline_CallLLM_HTTP5xxRetry) verifies that
HTTP 500 errors are retried and recover successfully.
This is a clean rebase of the approach originally proposed in #2768
by afjcjsbx.
程智超0668000959
99a7179e76