feat: invert quota usage markers when remaining mode enabled

[gsxdsm]

Summary

• In header and layout usage components, the expected usage marker now inverts when quotaDisplayMode is set to remaining
• All markers correctly reflect remaining quota instead of used quota across Header, VSCodeLayout, and UsageCard
• Keeps existing behavior when quotaDisplayMode is not remaining

Why

• Improves clarity for users who view remaining quota rather than consumed percentage
• Aligns visual indicators with the selected quota display mode to avoid confusion
• Centralizes the inversion logic to prevent duplicate or inconsistent marker calculations across components

Testing

• Not run locally
• Manual: toggle quotaDisplayMode between default and remaining in the UI and verify markers invert as expected in all affected components (Header, VSCodeLayout, UsageCard)
• Automated: ensure unit tests covering calculateExpectedUsagePercent usage and displayMode handling pass (if tests exist for paceInfo and marker calculation)