gui/experiments: add custom colors for experiment windows

[fsagbuya]

ARTIQ Pull Request

Description of Changes

Adds support for custom title bar and windows color in the experiment windows. Users can now select, apply, and reset these colors from the context menu:

• Color handling added to _ArgumentEditor and _ExperimentDock to apply colors to widgets.
• Introduces _ThemedTitleBar style to override the MDISubWindow title bar.
• ExperimentManager manages color storage and retrieval, persisting them across sessions.
• Updated state save/restore to include colors.

TODO: clean up storage when experiments get deleted (Other PR)

Color Menu

Title Bar

Window

Dark Theme Example

Windows Minimized

Related Issue

#2576

Type of Changes

	Type
✓	✨ New feature

Steps (Choose relevant, delete irrelevant before submitting)

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[sbourdeauducq]

This appears to break the greyed default value in empty text entry boxes. Here is what it should look like:

[fsagbuya]

This appears to break the greyed default value in empty text entry boxes.

Updated. Here's the new look:

[dhslichter]

Would it be possible/straightforward to have the color highlighting only applied to the title bar, or to be able to choose different colors for the title bar and the rest of the window?

[fsagbuya]

Would it be possible/straightforward to have the color highlighting only applied to the title bar, or to be able to choose different colors for the title bar and the rest of the window?

Yes. See updated description.

[sbourdeauducq]

Looks like the colors[expurl] dictionary accumulates entries forever and is not cleared when experiments are removed?
What would be a good way to clean it up?

[sbourdeauducq]

Sounds very hacky (and potentially leading to obscure behavior) that state only gets cleaned up at this point.

[sbourdeauducq]

Please explain the state cleanup strategy in source code comments.

[sbourdeauducq]

Considering the cases of experiments inside and outside repos.