Add mobile app, map-core, nearby sync, and activity recording specs

mobile-app: Unified React Native + Expo app combining Planner and
Journal. OAuth2 PKCE auth, MapLibre maps, versioned REST API with
Zod schemas, configurable server URL, offline SQLite, Web Push relay
notifications. TanStack Query + Zustand state management. Jest +
Maestro testing. 76 tasks across 5 phases.

map-core-package: Extract renderer-agnostic map definitions (tiles,
color palettes, POI categories, z-index) into @trails-cool/map-core.
Pure refactor preparing for MapLibre on mobile. 27 tasks.

mobile-activity-recording: GPS recording, live stats, HealthKit/Health
Connect export. Separated from mobile-app for independent scheduling.

mobile-nearby-sync: BLE route sync between nearby devices for offline
group riding. QR waypoint sharing as simpler v1. TXQR noted as future.

journal-rest-api spec: Full API contract — endpoints, auth, pagination,
errors, discovery, versioning, BRouter proxy.

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

openspec/changes/mobile-activity-recording/proposal.md

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+## Why
+
+The mobile app (when built) will show routes and allow editing, but won't record activities. Users want to track their rides/hikes with GPS, see live stats, and save recordings as Journal activities. This is a separate feature that depends on the mobile app foundation being in place first.
+
+## What Changes
+
+- GPS track recording via expo-location (foreground + background)
+- Live stats overlay (distance, duration, speed, elevation gain)
+- Save recorded track as GPX → Journal activity linked to the active route
+- HealthKit (iOS) / Health Connect (Android) export
+- Discard/pause/resume recording flow
+
+## Capabilities
+
+### New Capabilities
+- `mobile-activity-recording`: GPS recording, live stats, save as activity, health platform export
+
+## Impact
+
+- Depends on `mobile-app` change being implemented first
+- New dependencies: expo-location, expo-health
+- Background location permissions needed (App Store privacy review)