[P6.8.2] Frontend major-dependency upgrades: jest 30, jsdom 30, eslint 10, tailwind 4

[frankbria]

Summary

Four Dependabot PRs are major-version frontend upgrades that require manual migration — they fail real frontend tests (not just the spurious claude-review bot check) and/or carry known breaking changes. Held out of the routine dependency sweep and tracked here.

Dependabot PR	Bump	Status / blocker
#639	eslint 9 → 10	Fails Frontend Unit Tests + Test Summary (flat-config / plugin-compat changes)
#640	tailwindcss 3 → 4	Major breaking (CSS-first config, new PostCSS pipeline). CI currently masks the breakage because frontend-tests doesn't run npm run build (see #646) and Jest doesn't render CSS
#641	jest-environment-jsdom 29 → 30	Fails Frontend Unit Tests + Test Summary
#642	jest + @types/jest (29 → 30)	Fails Frontend Unit Tests + Test Summary

Notes

• chore(deps-dev): bump jest-environment-jsdom from 29.7.0 to 30.4.1 in /web-ui #641 and chore(deps-dev): bump jest and @types/jest in /web-ui #642 are the same Jest 30 ecosystem move and should be done together.
• Tailwind v4 (chore(deps-dev): bump tailwindcss from 3.4.19 to 4.3.1 in /web-ui #640) should be sequenced after [P6.5.1] frontend-tests CI: add npm run build + re-enable frontend lint #646 (add npm run build to CI) so the migration is actually verified by CI.
• These do not block a beta tag; they're maintenance/upgrade work.

Plan

• Jest 30 + jsdom 30 together: bump, fix breaking test API changes, green npm test.
• ESLint 10: migrate config, clear new rule violations, green lint (depends on lint being re-enabled in CI, [P6.5.1] frontend-tests CI: add npm run build + re-enable frontend lint #646).
• Tailwind 4: follow the v3→v4 upgrade guide, verify with npm run build (after [P6.5.1] frontend-tests CI: add npm run build + re-enable frontend lint #646).
• Close/supersede the corresponding Dependabot PRs (chore(deps-dev): bump eslint from 9.39.2 to 10.5.0 in /web-ui #639, chore(deps-dev): bump tailwindcss from 3.4.19 to 4.3.1 in /web-ui #640, chore(deps-dev): bump jest-environment-jsdom from 29.7.0 to 30.4.1 in /web-ui #641, chore(deps-dev): bump jest and @types/jest in /web-ui #642) as each lands.

Source: release-readiness dependency sweep 2026-06-13.

[coderabbitai]

🔗 Related PRs

#154 - fix: Add missing data-testid attributes for E2E tests [merged]
#187 - refactor: Consolidate web-ui test files to tests/ directory [merged]
#211 - feat(dashboard): Add PhaseProgress component for phase visualization [merged]
#498 - feat(web-ui): task dependency graph visualization in detail modal (#476) [merged]
#632 - chore(ci): supply-chain hardening — SHA-pin actions, dependabot, deploy gate [closed]

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