fix: resolve 4 bugs in termui

[saurabhhhcodes]

Description

This PR fixes real bugs found in the codebase:

• 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.
• Added Number.EPSILON to Math.round: prevents floating-point drift (e.g. 1.005 * 100 rounding to 100 instead of 101).
• Simplified empty-string validation: comparing trim() to '' misses whitespace-only input; .trim().length === 0 is explicit.

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: #3657

Summary by CodeRabbit

• Bug Fixes
  • Improved calculator handling for invalid numeric input.
  • Corrected Pomodoro timer progress percentage rounding.
  • Improved frame capture handling when trailing rows contain whitespace.

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes update numeric validation in the calculator, floating-point rounding in the pomodoro timer, and whitespace-only row detection in the development server.

Changes

Validation and display corrections

Layer / File(s)	Summary
Numeric validation and rounding examples/calculator/src/index.tsx, examples/pomodoro-timer/src/index.tsx	safeEval now uses Number.isNaN. The pomodoro percentage calculation adds Number.EPSILON before rounding.
Trailing frame-row detection packages/dev-server/src/devtools.ts	captureFrame checks the trimmed row length to identify whitespace-only trailing rows.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• Karanjot786/TermUI#3592: Overlaps with all three validation, rounding, and whitespace-detection changes.
• Karanjot786/TermUI#3418: Relates to the numeric and trimmed-string validation changes.
• Karanjot786/TermUI#3520: Overlaps with the calculator validation and pomodoro rounding changes.

Suggested labels: type:bug, area:examples, area:dev-server

Suggested reviewers: karanjot786

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the change as a bug fix and accurately summarizes the pull request.
Description check	✅ Passed	The description explains the bug fixes, identifies the change type, states testing, and references the related issue.
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

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@examples/pomodoro-timer/src/index.tsx`:
- Line 185: Update the percentage calculation in the label expression of the
relevant timer rendering method to add Number.EPSILON to this._value before
multiplying by 100, preserving the existing rounding and formatting behavior.
Add a regression test covering this._value = 0.145 and assert that the displayed
label is 15%.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: dd67ae93-b310-4cc8-99e2-95a633f2d7ef

📥 Commits

Reviewing files that changed from the base of the PR and between 6c7584e and e899eb7.

📒 Files selected for processing (3)

• examples/calculator/src/index.tsx
• examples/pomodoro-timer/src/index.tsx
• packages/dev-server/src/devtools.ts

[coderabbitai]

🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Move Number.EPSILON before the percentage scale.

At this._value = 0.145, the product can be 14.499999999999998. Adding Number.EPSILON after multiplication may still leave the value below 14.5, so the label can display 14% instead of 15%.

Add the epsilon before multiplying by 100, and add a regression test for this boundary.

Proposed fix

-        const label = this._showLabel ? ` ${Math.round(this._value * 100 + Number.EPSILON)}%` : '';
+        const label = this._showLabel ? ` ${Math.round((this._value + Number.EPSILON) * 100)}%` : '';

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@examples/pomodoro-timer/src/index.tsx` at line 185, Update the percentage
calculation in the label expression of the relevant timer rendering method to
add Number.EPSILON to this._value before multiplying by 100, preserving the
existing rounding and formatting behavior. Add a regression test covering
this._value = 0.145 and assert that the displayed label is 15%.