fix(frontend): resolve stash pop conflict in cluster drawer

[aGallea]

Summary

• resolve the stash-pop merge in the cluster drawer frontend by keeping the upstream drill-down behavior
• restore the drawer regression coverage for sub-cluster palette colors with a stable legend swatch test id
• exclude unrelated local screenshots and docs from the branch so the PR stays focused

Test Plan

• uv run pytest
• cd frontend && npm run build
• cd frontend && npx playwright test e2e/cluster-drawer.spec.ts
  • blocked on the existing local server state when reusing port 8000 during verification; 26/27 tests passed and the new swatch assertion should be rechecked in a fresh app session

[github-actions]

Tests Report 📄

Tests Succees ✅

JUnit Details

Total Tests	Failures	Errors	Skipped	Time ⏳
250	0	0	0	62.13s

Coverage Details ☑️

No coverage details to present