[Roadmap] Finalize JOSS paper — response to reviewers

## Objective

Finalize the JOSS paper for OptimalControl.jl — respond to reviewer comments and get the paper accepted.

## Context

The JOSS paper is on the [joss branch](https://github.com/control-toolbox/OptimalControl.jl/tree/joss/joss). The [JOSS review](https://github.com/openjournals/joss-reviews/issues/10630) is in progress. The response to reviewers ~~needs to be completed~~ is completed.

## Related issues and PRs

Addressing reviewer feedback has led to the following issues and PRs:

**Issues:**
- https://github.com/control-toolbox/OptimalControl.jl/issues/795
- https://github.com/control-toolbox/OptimalControl.jl/issues/799
- https://github.com/control-toolbox/OptimalControl.jl/issues/802
- https://github.com/control-toolbox/OptimalControl.jl/issues/803
- https://github.com/control-toolbox/OptimalControl.jl/issues/805

**Pull requests:**
- https://github.com/control-toolbox/OptimalControl.jl/pull/762
- https://github.com/control-toolbox/OptimalControl.jl/pull/804
- https://github.com/control-toolbox/OptimalControl.jl/pull/813

## Why

Publication in JOSS (Journal of Open Source Software) provides academic recognition and visibility for the control-toolbox ecosystem. It also serves as a citable reference for users.

## References

- [JOSS branch](https://github.com/control-toolbox/OptimalControl.jl/tree/joss/joss)
- [JOSS review issue](https://github.com/openjournals/joss-reviews/issues/10630)
- [Roadmap comment](https://github.com/orgs/control-toolbox/discussions/68#discussioncomment-17584843)