Summary

Adds an optional numberFormat parameter to the existing formatCells tool, allowing callers to control how cell values are displayed and — importantly — to clear persistent number formats that survive a standard formatting reset.

Motivation

Google Sheets auto-parses strings like "3/9" as dates when written with USER_ENTERED value input. This applies a date number format to the cell. Subsequent formatCells calls that reset bold, fontSize, and backgroundColor do not clear the number format, because numberFormat wasn't included in the fields mask. As a result, integer values written to those cells in later runs would display as 1900-era dates (e.g. 9 → "1/9" because January 9, 1900 is serial number 9).

Setting numberFormat: { type: "TEXT" } explicitly resets the cell to plain text, clearing the lingering date format.

Changes

• formatCells.ts: Adds numberFormat as an optional Zod object parameter with type (enum) and optional pattern (string). Updated description. Added to the "at least one option" refine check.
• googleSheetsApiHelpers.ts: Added numberFormat to the format type. When present, sets userEnteredFormat.numberFormat and dynamically includes numberFormat in the fields mask so it's actually written (not just skipped).

API

numberFormat?: {
  type: 'TEXT' | 'NUMBER' | 'PERCENT' | 'CURRENCY' | 'DATE' | 'TIME' | 'DATE_TIME' | 'SCIENTIFIC';
  pattern?: string; // e.g. "0.00", "#,##0", "yyyy-MM-dd"
}

• type: "TEXT" — treats cell as plain text; clears any existing date/number format
• type: "NUMBER" — general numeric display
• pattern — optional custom format code; if omitted, the type's default display is used

Test plan

• Write "3/9" with USER_ENTERED, confirm it becomes date-formatted. Then call formatCells with numberFormat: { type: "TEXT" } and verify integer values in those cells display as plain numbers.
• Apply numberFormat: { type: "NUMBER", pattern: "0.0" } — verify one decimal place display
• Apply numberFormat: { type: "DATE", pattern: "yyyy-MM-dd" } — verify date display
• Confirm existing bold/fontSize/backgroundColor resets still work when numberFormat is not passed (fields mask is unchanged for those calls)
• Confirm Zod accepts numberFormat alone as a valid "at least one option" case

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