feat: add accessible tooltip primitive to MarketCard

[webmirroring]

Closes #365

Summary

• Added app/components/Tooltip.tsx, a reusable accessible tooltip primitive with hover delay, keyboard focus support, Escape dismissal, touch long-press support, role="tooltip", and aria-describedby wiring only while the tooltip is rendered.
• Used the primitive across the marketing MarketCard odds, pool, and ending-time metadata so those compact values have accessible explanatory text.
• Added focused tests covering delayed hover, focus/Escape, touch long-press, and the aria-describedby relationship.

Validation

• PASS: /Users/codoon/.cache/codex-runtimes/codex-primary-runtime/dependencies/node/bin/node node_modules/jest/bin/jest.js --runTestsByPath 'app/(marketing)/_components/__tests__/markets-widget.test.tsx' --runInBand
• PASS: /Users/codoon/.cache/codex-runtimes/codex-primary-runtime/dependencies/node/bin/node node_modules/eslint/bin/eslint.js 'app/components/Tooltip.tsx' 'app/(marketing)/_components/markets-widget.tsx' 'app/(marketing)/_components/__tests__/markets-widget.test.tsx'
• PASS: git diff --check

Existing repo-level blockers observed

• tsc --noEmit currently fails on unrelated existing files, including missing ResolutionPreview, ErrorBoundary, shareProfile, getKit, and existing PredictionCard outcome/category references.
• Full Jest currently has unrelated existing failures: 16 suites failed / 54 passed, 74 tests failed / 539 passed. Examples include connect-wallet-modal missing getKit, event form label associations, and settings tests missing PrivacyProvider.
• Full next lint currently fails on unrelated existing files such as activity-timeline-demo, EventDetailsClient, layout, PredictionCard.test.tsx, and several react/no-unescaped-entities issues. The files touched in this PR pass direct ESLint.

[vercel]

@beihaiguaishou is attempting to deploy a commit to the Jagadeesh B's projects Team on Vercel.

A member of the Team first needs to authorize it.