test: add displacement and profile tests

[yoreley777]

Summary

Adds Playwright coverage for:

• Displacement
  • velocity layer
  • flight direction toggle
  • draw point
  • highlight series
  • delete series
  • delete all series
  • no points selected
  • select multiple points
• Profile
  • dark mode
  • login state sync across instances

Related Issues

N/A

Screenshots / UI Changes

N/A

i18n

N/A

Tests & Build

• npm run lint passes
• npm test passes (or N/A)
• npm run build succeeds

Notes

Some larger Ghost Inspector tests were split into smaller, focused specs:

• Layer Cumulative Velocity Asc & Desc was covered as velocity-layer.spec.ts and flight-direction-toggle.spec.ts
• AOI Interaction Test: Draw, Highlight & Delete was covered as draw-point.spec.ts, highlight-series.spec.ts, delete-series.spec.ts, and delete-all-series.spec.ts

login-state-sync.spec.ts uses two pages in the same browser context and a mocked auth cookie response to verify BroadcastChannel-based sync behavior.

Possible follow-up: add coverage for logout state syncing across instances.