fix: resolve 4 bugs in termui

[saurabhhhcodes]

Description

This PR fixes real bugs found in the codebase:

• Added explicit radix to parseInt: without 10, strings like '0x1F' or '08' parse in unintended bases.
• Simplified empty-string validation: comparing trim() to '' misses whitespace-only input; .trim().length === 0 is explicit.
• Replaced global isNaN with Number.isNaN: the global version coerces its argument, so isNaN('1') returns false while Number.isNaN is strict.
• Fixed default sort: .sort() coerces elements to strings, so [10, 9, 2] sorts as [10, 2, 9]; numeric comparator sorts correctly.

Type of Change

• Bug fix (non-breaking change fixing an issue)

How Has This Been Tested?

• Local manual testing

Checklist

• My code follows the style guidelines
• I have performed a self-review

Related Issue

Ref: #3515

Summary by CodeRabbit

• Bug Fixes
  • Improved negative-number validation in the calculator.
  • Fixed tab-key handling in the widget gallery for consistent tab switching.
  • Corrected multi-select option ordering when selections include multiple-digit indices.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8103e784-b90f-4b3c-8672-98e1d099511d

📥 Commits

Reviewing files that changed from the base of the PR and between 6c7584e and b97645f.

📒 Files selected for processing (3)

• examples/calculator/src/index.tsx
• examples/widget-gallery/src/index.ts
• packages/ui/src/MultiSelect.ts

---

📝 Walkthrough

Walkthrough

The changes make numeric validation, parsing, and sorting explicit in the calculator example, widget gallery, and multi-select component.

Changes

Numeric handling corrections

Layer / File(s)	Summary
Calculator negative-number validation examples/calculator/src/index.tsx	safeEval now uses Number.isNaN(Number(tokens[1])).
Widget gallery key parsing examples/widget-gallery/src/index.ts	WidgetGalleryApp.handleKey now calls parseInt with radix 10.
Multi-select option ordering packages/ui/src/MultiSelect.ts	selectedOptions now sorts checked indices numerically before mapping them to options.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• Karanjot786/TermUI#3413: Updates WidgetGalleryApp.handleKey to use an explicit radix.
• Karanjot786/TermUI#3487: Applies related numeric parsing and validation corrections.
• Karanjot786/TermUI#3496: Updates multi-select indices to use numeric sorting.

Suggested reviewers: karanjot786

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the fixes and testing, but it omits the required package section and uses “Ref: #3515” instead of “Closes #”.	Add the affected package names, change the issue reference to “Closes #3515”, and complete the required template sections and checklist.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the pull request as a bug fix for four TermUI bugs.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}