[email-rotation] give extend_rotation an --ensure-weeks flag

[gburgessiv]

This allows for easy cronjob writing. You can e.g., automatically --ensure-weeks=16 every month, and extend_rotation.py will handle making sure that you always have rotations covering up to a quarter out.

Tested by running locally on a few different values of --ensure-weeks.

[Copilot]

Pull Request Overview

This PR adds a new --ensure-weeks flag to the extend_rotation.py script, allowing users to specify how many weeks into the future the rotation schedule should cover. This enables automated cronjob usage where you can ensure a consistent coverage period (e.g., 16 weeks for quarterly planning) rather than adding a fixed number of rotations.

• Replaces fixed --num-rotations parameter with mutually exclusive --num-rotations and --ensure-weeks options
• Adds calculate_rotations_to_cover() function to determine how many rotations are needed for a given time period
• Updates the main logic to calculate required rotations based on the chosen flag

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
extend_rotation.py	Implements the new --ensure-weeks flag with supporting logic and argument parsing changes
extend_rotation_test.py	Adds comprehensive test coverage for the new calculate_rotations_to_cover() function

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[gburgessiv]

Hey @kbeyls, would you be willing to TAL at this really fast, since you looked over the initial code drop? :)

Will squash the copilot fixup commit away when I go to merge.

[kbeyls]

LGTM, thank you!

[gburgessiv]

Thanks for your reviews!