Task group 3 of gpx-parser-robustness. Timestamps were passed through raw;
a partially-broken time channel from a flaky recorder silently shrank
moving time and skewed start-time derivation.
New pure `timestamp-repair.ts` applied per segment after parsing:
- validity = Date.parse yields a finite epoch;
- a segment with no valid timestamps is left untouched (untimed track);
- >50% invalid → drop all the segment's timestamps (noise, not signal);
- otherwise → linearly interpolate invalid runs between valid neighbours
(by point index), leading/trailing runs clamp to the nearest valid
timestamp; only repaired points are rewritten as ISO 8601, valid points
keep their original string.
Monotonicity intentionally not enforced (movingTime already skips
non-positive intervals; reordering would be fabrication). No GpxData shape
change. Wired into parseTracks output in parse.ts.
Verified: gpx typecheck + lint clean, 81/81 tests pass, journal + planner
typecheck unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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