chore(analytics): document that screenName must be non-empty in trackScreenView/trackScreenLeave

[rahul-mixpanel]

Summary

• Update JSDoc on screenName param for trackScreenView and trackScreenLeave in index.js stating it must be non-empty and the event is silently dropped if empty/whitespace-only.
• Add JSDoc to TypeScript definitions in index.d.ts for the same methods.
• Run prettier on changed files.

Test plan

• Verify JSDoc renders correctly in IDE hover tooltips

SDK-142

[linear-code]

SDK-142

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
index.js	Adds documentation for the existing screen-name validation behavior.
index.d.ts	Adds matching API documentation to the TypeScript declarations.

_{Reviews (2): Last reviewed commit: "Revert "chore: run prettier on index.js ..." | Re-trigger Greptile}