Rename ring mode coefficients to ring mode index

[deleon117]

No description provided.

[Copilot]

Pull Request Overview

This PR renames the ring mode coefficients terminology to ring mode index for better clarity. The change updates both the enum name and field name to reflect that these values represent indices rather than coefficient sets.

• Renamed RingModeCoefficientSets enum to RingModeIndex with corresponding value name updates
• Updated the field in MachineSettings from ring_mode_coefficient_set to ring_mode_index
• Incremented version from 5.1.2-dev0 to 5.1.3-dev0

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
ansys/api/additive/v0/additive_domain.proto	Renamed enum and field to use "index" terminology instead of "coefficient"
ansys/api/additive/VERSION	Version bump to reflect the API change

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}