feat(ui): add stacked vertical terrain gradient and target pace VU meters

[dkhawk]

Summary

Adds stacked vertical retro stereo volume-style VU meters on the side of the 3D map viewport to visualize terrain gradient and target pace, while keeping the bottom elevation profile chart clean and intact.

Key Changes

• Vertical Dual VU Meters (VerticalTerrainVisualizer): Adds floating vertical Canvas VU columns directly beneath the spatial compass gauge (#whiskey-compass).
  • Grade Bar Graph: Features center 0% baseline mark. Descents (< 0%) illuminate downward in Emerald Green (#10b981). Climbs (> 0%) illuminate upward in Blue, Amber, Orange, Red, or Crimson.
  • Pace Bar Graph: Stacked directly below the Grade bar graph. Visualizes active sector strategy target pace (sec.target_pace_min) across 30 vertical LED blocks.
• Course Studio Tab Consolidation: Moves Weather Forecast and Safety Alerts dialogs to be dedicated tabs inside the master Course Architect & Studio dialog (card-importer) to eliminate overlapping floating panels.
• Dismissible Viewport Controls: Adds close buttons (×) directly on the spatial compass and vertical VU meters panels, alongside quick toggle restoration buttons in the top HUD header.
• Test Validation: Adds unit tests validating pace classification and gradient tier alignment, verifying 25/25 automated unit tests passing (node --test test/gpx.test.js).