chore: test JSONPath queries and schema validation

[kudala-bharani]

What and why

Adds 20 tests for the JSONPath and JSON Schema helpers. They cover empty and invalid inputs, the sample queries and their paths, no-match results, and validation errors for required properties, minimum values, and string lengths.

Branched from the latest develop, including the Vitest 4 upgrade. Only the two test files changed.

Closes #97

Type of change

• Bug fix
• New tool or feature
• Tests
• Refactor or cleanup
• Docs

Checklist

• npm run lint && npm run test && npm run build passes locally
• Logic changes live in lib/ and have a test in lib/__tests__/ — tests only; no logic changes
• No analytics, trackers, or calls that send user data off-device
• Works in both light and dark themes (if UI changed) — not applicable
• Inputs have labels and it works with the keyboard alone (if UI changed) — not applicable
• New tool: registry entry, page.tsx, client component, opengraph-image.tsx, and the bug report dropdown are all done — not applicable

Notes for reviewers

Verified with Node 22.23.3 and Vitest 4.1.11: all 85 tests pass, lint exits successfully, and the production build passes. Lint still reports 13 warnings in unchanged files; the two new test files pass with zero warnings.

[anurag629]

Hey @kudala-bharani, nice work again! This covers everything in #97, and I like that the error tests check the exact parse messages for both empty data and an empty schema. CI is green, merging this now.

If you want another one, just comment on any open hacktoberfest issue and I'll assign it to you.