chore: add testing sheet local run

[snowystinger]

Closes

Adds the capability to run the testing sheet generator locally and save out to a file. This makes it easier to run for a custom set of dates.

GITHUB_TOKEN=<gh token> node scripts/sendWeeklyExcelSheet.mjs --local 2026-07-01 2026-07-08

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[rspbot]

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