Task groups 1–2 of gpx-parser-robustness. The parser trusted its input:
`parseFloat(attr ?? "0")` turned a missing lat/lon into a 0,0 Null Island
point (which passes range validation) and garbage into NaN that poisoned
distance and gain/loss totals; `<rte>`/`rtept` files (Garmin courses, many
exporters) parsed to zero track points and were rejected.
- `parsePoint`: skip a trkpt/rtept whose lat/lon is missing or non-finite
(no more 0,0 default); a non-finite `<ele>` becomes `undefined` so it
never leaks NaN into totals. Parsing stays parseFloat-lenient (trailing
junk like `471.0m` still accepted), gated by Number.isFinite.
- Drop segments left with fewer than 2 points (render nothing / break
distance math).
- Parse `<rte>` as track segments appended after `<trk>` segments, rtept
handled identically — route-only files now import.
No GpxData shape change; well-formed files parse identically. Updated the
geom single-point test to the new drop-invariant.
Verified: gpx typecheck + lint clean, 76/76 tests pass, journal + planner
typecheck unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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