Fix time parsing and AM/PM conversion inconsistencies

[ibrahim-sadiqi]

Description

This PR fixes time parsing inconsistencies to better align with Excel’s behavior.

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Fixes

1. Time Parsing – "4:"

• Previously, inputs like "4:" returned null
• Now correctly parsed as time using inferred h:mm format (locale-aware), consistent with Excel behavior

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2. Incorrect AM/PM Conversion

• Fixed incorrect handling of 12-hour time boundaries and AM/PM logic

Before:

• "12:00 AM" → 0.5 (incorrect, interpreted as PM)
• "12:00 PM" → 0.00 (incorrect, interpreted as AM)
• "12:30 PM" → ~0.21 (incorrect fractional value)

After:

• "12:00 AM" → 0.00 ✅
• "12:00 PM" → 0.5 ✅
• "12:30 PM" → ~0.52 ✅

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Summary

• Corrected AM/PM boundary handling (12 AM / 12 PM edge cases)
• Added support for parsing incomplete time inputs like "4:"

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Notes

These fixes improve compatibility with real-world spreadsheet inputs and reduce discrepancies when interpreting time values.