Fixes#5862.
The Hermes ACP provider-error sniffer over-matched conversation/tool JSON that
Hermes echoes to stderr as `[INFO] root:` records, flipping already-completed
runs to failed. Error matching is now scoped to real provider-error boundaries:
- Skip INFO/DEBUG root-logger records (single- and multi-line JSON) via a
structural state machine, so echoed payloads never participate in matching.
- Keep genuine bare provider errors (⚠️/❌/📝 Error:) and non-root [ERROR]
records, including after a possibly-truncated INFO record.
- Length only bounds the persisted error summary, never whether a line is
classified as an error (fixes the earlier #1952-style regression).
Reported and initial fix by @YikaJ; remaining boundary fixes added directly by
the maintainers to land this quickly as a production bug.
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