Task group 4 of gpx-parser-robustness. Many apps put the only
human-readable title on the <trk>/<rte>, not in <metadata>.
- name/description now fall back to the first <trk>/<rte>'s <name>/<desc>
when <metadata> lacks them (<metadata> still wins when present).
- that track/route's <cmt> is appended to the description (blank-line
separated) when present and not already identical (OM BuildDescription
dedup); used as the description outright when there's no <desc>.
`directChildText` reads direct-child text without relying on `:scope`
(portable across the jsdom + linkedom paths). No GpxData shape change;
well-formed files with metadata are unaffected.
Verified: gpx typecheck+lint clean, 87/87; full `pnpm test` 11/11;
journal + planner typecheck unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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