fix(nitro): Capture errors only through the Nitro error hook (#24952)

Capture errors through Nitro's error hook so ordinary thrown errors are
reported once and 3xx/4xx HTTP errors stay filtered. The tracing channel
continues recording span error status without sending a separate error
event.

Adds E2E coverage for an explicitly thrown 400 and updates the standard
error test to expect the hook event.

Fixes #24939

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Co-authored-by: OpenAI Codex <codex@openai.com>