gui: ensure stable color ordering between compilers

[gadfort]

Summary

Ensure both clang and gcc generate the same color sequence.
Per claude:

GCC typically evaluates function arguments right-to-left.
Clang typically evaluates them left-to-right.

Type of Change

• Bug fix

Impact

Bazel and CMake builds will have the same colors.

Verification

• I have verified that the local build succeeds (./etc/Build.sh).
• I have run the relevant tests and they pass.
• My code follows the repository's formatting guidelines.
• I have signed my commits (DCO).

[gemini-code-assist]

Code Review

This pull request updates the generate_next_color lambda in displayControls.cpp to evaluate the random color components (blue, green, and red) in a deterministic sequence before constructing the QColor object. This prevents unspecified evaluation order of arguments in the QColor constructor. There are no review comments, and we have no additional feedback to provide.

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