Fix mutability issue leading to wrong behavior in //ascend and //descend

[SirYwell]

Overview

Description

//ascend and //descend functionality used a mutable vector, but the vector got modified in another method. This caused the commands to misbehave. Simply reverting to the original WE code fixes that. As this isn't performance critical, using immutable vectors seems to be fine.

### Submitter Checklist
- [x] Make sure you are opening from a topic branch (**/feature/fix/docs/ branch** (right side)) and not your main branch.
- [x] Ensure that the pull request title represents the desired changelog entry.
- [x] New public fields and methods are annotated with `@since TODO`.
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