fix(logs): detect high-precision epoch timestamps

[efegokdemir]

Closes #74.

Summary

Detect microsecond- and nanosecond-precision Unix epoch values during log field detection.

Implementation

• Recognize epoch values by precision range rather than only 10- and 13-digit widths.
• Convert with BigInt before converting to milliseconds, avoiding precision loss for nanosecond values.
• Validate the resulting date is within the existing 2000–2100 plausibility window.
• Reject values outside supported precision ranges and implausible high-precision values.
• Preserve rejection of ordinary small integers and unrelated date formats.

Regression tests

Added coverage for valid 16-digit microsecond and 19-digit nanosecond timestamps, plus implausible 16- and 19-digit values.

Testing

• npm run check — not run: Node/npm is unavailable in this environment.
• npm run build — not run: Node/npm is unavailable in this environment.
• npm test -- --run src/lib/logFieldDetector.test.ts — not run: Node/npm is unavailable in this environment.
• git diff --check — passed.

AI disclosure

AI assistance was used during investigation and implementation; the change and validation results were reviewed before submission.

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[efegokdemir]

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[efegokdemir]

All contributors have signed the CLA. Thanks!

[efegokdemir]

The only failed check is the old CLA signed run from 2026-09-26. The CLA bot subsequently reported that all contributors have signed, and the author confirmed the CLA on 2026-09-30. I attempted to rerun the failed job, but GitHub requires repository-admin permission. Please rerun the CLA workflow from the repository side.