Error doc inflation

[jenbreese]

READY FOR REVIEW

Notes: I added the errors in the error doc. I also updated some of the UI to match the new styles we are doing. I brought up some of the consistency issues.

Summary

Inflation Impact Calculator -- validation, formatting, and accessibility

Validation

• Added empty field error: blocks calculation and shows "Enter an initial amount to see the impact of inflation over time."
• Added range error for values outside $0.01 and $1,000,000,000: blocks calculation and shows "Enter an amount between $0.01 and $1,000,000,000."
• Results panel shows "—" when the field is empty or out of range
• Sliders retain their existing enforced ranges; no changes needed there

Formatting

• Initial price input now displays comma-formatted values (e.g. 1,000,000)
• Input strips commas on focus for clean editing and re-applies them on blur
• Results panel uses formatCurrency via Intl.NumberFormat for consistent USD output, matching the PV calculator pattern

Accessibility

• Error message <p> is always rendered and referenced via aria-describedby; hidden with sr-only when no error is active, visible when one is
• aria-invalid set on the input when an error is present
• Results panel wrapped in aria-live="polite" aria-atomic="true" so screen readers announce updates
• Both sliders have aria-label, aria-valuemin, aria-valuemax, aria-valuenow, and aria-valuetext
• Time period display span has aria-live="polite" so the year count is announced as the slider moves
• Slider min/max label spans marked aria-hidden="true" since the range is already conveyed via ARIA attributes
• $ symbol positioned with top-1/2 -translate-y-1/2 replacing the non-standard top-8.5