Update specs with waypoint hover, day interaction, per-day export
Proposal: Added waypoint highlighting, Journal day interaction, and
per-day GPX export to What Changes and Impact sections.
Design: Added D13 (sidebar waypoint hover → map marker scale), D14
(Journal day segment hover with fly-to-bounds), D15 (per-day GPX
export endpoint with ?day=N query param).
Tasks: Added sections 8 (Planner waypoint hover, 2 tasks), 9 (Journal
day interaction, 5 tasks). Renumbered testing to section 10.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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