feat(frontend): keyboard navigation for GlobalSearch results

[Bill-tech1]

Closes #123

---

Summary

Adds correct Up/Down Arrow keyboard navigation to the GlobalSearch component and sets up the frontend unit test infrastructure.

Problem

The existing handleKeyDown used modulo arithmetic for navigation:

setActiveIndex((i) => (i + 1) % total);   // ArrowDown
setActiveIndex((i) => (i - 1 + total) % total); // ArrowUp

This had two bugs:

1. Empty results crash – when total === 0, % 0 produces NaN, corrupting activeIndex state.
2. Wrapping – ArrowDown on the last item jumped back to the first; ArrowUp on the first item jumped to the last. The requirement is to stay within bounds.

Changes

packages/frontend/src/components/GlobalSearch.tsx

Replaced modulo navigation with clamped navigation guarded by an empty-results check:

// Before
setActiveIndex((i) => (i + 1) % total);
setActiveIndex((i) => (i - 1 + total) % total);

// After
if (total > 0) setActiveIndex((i) => Math.min(i + 1, total - 1));
if (total > 0) setActiveIndex((i) => Math.max(i - 1, 0));

All existing behaviour (mouse clicks, Enter to select, Escape to close, Ctrl+K shortcut, search history, accessibility attributes) is preserved unchanged.

Test infrastructure (new)

• vitest@1 + @testing-library/react + jsdom added as devDependencies
• vite.config.ts extended with a test block (environment: 'jsdom', globals, setupFiles)
• test / test:watch scripts added to package.json
• src/test/setup.ts imports @testing-library/jest-dom matchers

packages/frontend/src/components/__tests__/GlobalSearch.test.tsx (new)

10 tests across two suites:

Suite	Tests
GlobalSearch keyboard navigation	renders input; ArrowDown on empty results (no throw); ArrowUp on empty results (no throw); Escape closes dropdown; focus opens dropdown
keyboard navigation clamping logic	ArrowDown clamps at last index; ArrowUp clamps at first index; ArrowDown from -1 moves to 0; no navigation when total=0; old modulo-on-zero bug demonstrated

packages/frontend/.eslintrc.cjs (new)

The root .eslintrc.js references @typescript-eslint/recommended but the package was not resolvable from the workspace root, making pnpm lint fail with a config error before this PR. A frontend-specific config is added so pnpm lint runs cleanly.

Testing

pnpm --filter @stellar-analytics/frontend lint    # ✅ 0 errors, 0 warnings
pnpm --filter @stellar-analytics/frontend test    # ✅ 10/10 tests pass
pnpm --filter @stellar-analytics/frontend type-check  # pre-existing errors only (14, all in unrelated files, confirmed present on main)

Notes

• No regressions introduced. All pre-existing type errors were confirmed to exist on main before this branch.
• No new dependencies beyond the test toolchain.

[drips-wave]

@Bill-tech1 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits