Diagnostics: classify provider runner failures

[gaofeng21cn]

Problem

Runner failures currently expose some deterministic local errors, but provider account/quota blockers and transient upstream provider errors are not separated clearly enough. Retry-exhausted events also lack a structured diagnosis payload, making daemon and doctor follow-up harder.

Solution

• Add generic Codex provider diagnostics for account/quota/billing/credential blockers and transient upstream provider failures.
• Treat provider account blockers as non-retryable so the daemon stops blind retries and surfaces actionable guidance.
• Preserve retry/backoff behavior for transient upstream provider failures, then park the quest with an external-provider continuation reason after retry exhaustion.
• Attach structured diagnosis payloads to runner.turn_retry_exhausted events and propagate diagnosis code/guidance to turn errors.
• Extend doctor coverage for provider account failures with problem/why/fix rendering.

MDS provenance

Adapted the generic runner-diagnostics parts of MedDeepScientist commits bdd6f6f, 2f584e7, and the generic diagnostic/doctor pieces of 838f87e. MedDeepScientist, MAS, medical-fork, manuscript-readiness, and publication-authority semantics were intentionally excluded.

Tests

• python -m py_compile src/deepscientist/diagnostics/runner_failures.py src/deepscientist/daemon/app.py src/deepscientist/doctor.py
• git diff --check
• uv run --with pytest pytest -q tests/test_runner_failure_diagnostics.py tests/test_daemon_api.py::test_daemon_retry_exhausts_after_five_attempts tests/test_daemon_api.py::test_daemon_retry_exhaustion_records_provider_diagnosis_payload tests/test_daemon_api.py::test_daemon_stops_retry_for_provider_account_blocker tests/test_daemon_api.py::test_daemon_skips_retry_for_non_retryable_minimax_protocol_error tests/test_daemon_api.py::test_daemon_skips_retry_for_unknown_binary_attachment_extension_error tests/test_doctor.py::test_doctor_reports_recent_runtime_failure_with_problem_why_fix tests/test_doctor.py::test_doctor_reports_provider_account_runtime_failure_with_problem_why_fix tests/test_doctor.py::test_doctor_surfaces_probe_diagnosis_for_known_tool_argument_error