Add visual redesign OpenSpec change with mockups and logo concepts

Design direction: D1 warmth + D3 lightness (warm off-whites, sage green,
Outfit + Geist Mono). Includes desktop + mobile HTML mockup, 5 logo
concepts, and 33 implementation tasks across 7 phases.

Logo decision: Waypoint Dot mark (3 connected dots) + wordmark combo.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/changes/visual-redesign/proposal.md

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+## Why
+
+The current UI is functional but unstyled — default Tailwind colors, no visual
+identity, no typography system. As features mature (route coloring, no-go areas,
+multiplayer), the app needs a design language that matches the quality of the
+interactions. Early testers find the tool powerful but visually generic.
+
+A design exploration produced a "Trail Worn warmth + Nordic Precision lightness"
+direction: warm off-whites, sage green accent, earthy overnight markers, Outfit
+font, Geist Mono for stats. The reference mockup lives at
+`mockup.html` (desktop + mobile views).
+
+## What Changes
+
+- **Design system**: CSS custom properties for colors, typography, spacing.
+  Tailwind config extended with project tokens. Outfit (body) + Geist Mono
+  (stats) fonts.
+- **Topbar redesign**: Logo with mountain mark, segmented color mode toggle,
+  participant avatars with names, "+ Invite" button, Export GPX right-aligned
+- **Sidebar redesign**: Route summary header (name, stats, duration), collapsible
+  day breakdown (aspirational, "SOON" badge), waypoints nested inside days,
+  overnight badges on stop waypoints, waypoint notes
+- **Map marker styling**: Olive/dark numbered circles instead of blue, "NIGHT"
+  badges on overnight stops, day segment labels on route
+- **Elevation chart**: Day dividers as dashed vertical lines, elevation gradient
+  matching route colors, km hover label, min/max elevation labels
+- **Mobile responsive**: Bottom sheet pattern replacing hidden sidebar, simplified
+  header, swipeable tabs (Days/Waypoints/Notes)
+
+## Capabilities
+
+### New Capabilities
+
+- `design-system`: Shared design tokens, typography, color palette, component
+  styling patterns for the Planner app
+
+### Modified Capabilities
+
+- `map-display`: New waypoint marker styling, overnight badges, day labels
+- `planner-session`: Sidebar layout with route summary and day breakdown
+
+## Impact
+
+- **Tailwind config**: Extended with project color tokens and font families
+- **All Planner components**: Updated styling (colors, typography, spacing)
+- **New fonts**: Outfit + Geist Mono loaded via Google Fonts or self-hosted
+- **No functional changes**: All existing interactions preserved, only visual
+- **ElevationChart**: Canvas drawing updated for new color gradient + day dividers
+- **Mobile**: New bottom sheet component for sidebar content