What changed

• persists the Sessions tray's right-hand detail scrollbar in addition to the existing session-list scrollbar
• stores detail scroll positions independently by session id
• restores the selected session and both navigation positions after a reload
• documents the behavior and adds preference/component coverage

Why

The Sessions tray has two independent scrolling regions. Only the left session list was persisted, so reloading could restore the selected ride while losing the rider's position within its detailed metrics and charts.

Impact

Riders return to the same session, list position, and detail position after reloading. Switching to another session does not inherit an unrelated ride's detail offset.

Validation

• bun run ci
• 218 tests passing
• Tailwind diagnostics
• TypeScript type check
• production Vite build