merge-train: read device failure records as written; a device failure is a devices problem, not a driver error (#91)

[thejackshelton]

The bug (#91's landing): the driver failed #91 at stage error with "packages/parity/out/device-failures-ios.json has an entry that is not { lane, case, dpr, node, kind }".

The validator in parseDeviceEvidence (scripts/merge-train-lib.ts) required node to be a string. But device-lanes.ts writes node: null for a failure of a whole case, such as a device record or a missing dump. #91's iOS host timed out, giving device-record failures with case "-" and node null. So the run's own failures threw, and the driver reported a driver error instead of judging them.

What changed:

• parseDeviceEvidence now accepts exactly the written shape, { lane, case, dpr, node: string | null, kind, detail: string }. It stays strict about everything else: a wrong type or an unknown key throws, naming the entry's index and contents. Both committed master files (ios 57, android 86 entries) match the shape.
• deviceRunProblems reports a failing lane readably:
  • a count per case and DPR (most first, at most 8);
  • then the first details;
  • both for "N failure(s) master does not have" and for a lane that now fails where master passed. The latter listed no failures before.
• scripts/land.ts judgeDevices: if the run's own records can't be read, that is now a judge-devices failure with the reason, not a driver error. Master's records stay a driver error.

What passed:

• pnpm typecheck passed.
• vitest run merge-train land passed (123 tests).
• New tests use real records: three entries copied from /tmp/dragon-land/packages/parity/out/device-failures-ios.json, plus INL1a 5/5 (C2): lowering inline boxes and <br>s, native runtime emit, 7 inline fixtures and lanes #91's device-record entry, rebuilt from its run log. Its detail, "the host did not finish: timed out after 1896 s waiting for the iOS host to finish", is verbatim. The tests cover:
  • parsing node null and detail;
  • refusing a non-string detail, a numeric node, and an unknown key;
  • the readable summary for a newly failing lane and for added failures;
  • truncation past 8 cases.
• Two existing tests were retargeted to the new messages, with the same intent: the problem text and the refusal text.

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