[codex] test ErrorBoundary fallback recovery

[prettyboyvic]

Summary

• add component tests for ErrorBoundary fallback rendering, theme classes, reset recovery, guarded logging, and production-safe details
• route caught errors through the shared guarded logger instead of raw console.error
• make the reset action recover the boundary without forcing a page reload
• restore Vitest's node_modules exclusion so the app test script does not collect dependency test files

Validation

• corepack pnpm@9.15.9 install --frozen-lockfile
• corepack pnpm@9.15.9 exec vitest run src/shared/components/ErrorBoundary.test.tsx (5 tests passed)
• corepack pnpm@9.15.9 test (16 files / 197 tests passed; existing jsdom stderr remains from current AuthContext and Leaderboard tests)
• corepack pnpm@9.15.9 exec prettier --check vite.config.ts src/shared/components/ErrorBoundary.tsx src/shared/components/ErrorBoundary.test.tsx
• corepack pnpm@9.15.9 exec eslint src/shared/components/ErrorBoundary.tsx src/shared/components/ErrorBoundary.test.tsx (0 errors; existing Fast Refresh warning on ErrorBoundary export shape)

Notes

• npm ci is blocked by the stale package-lock.json, so validation used the committed pnpm-lock.yaml with pnpm 9.
• corepack pnpm@9.15.9 typecheck cannot run because tsc is not installed in the project dependencies.

Closes #38