Add "Download Java" button to dialog & other small changes

[trustytrojan]

• The "Download Java" button is right next to the "Browse..." and "Test" buttons, it opens the OS browser to the Adoptium Temurin Java 25 download page, or displays a link in a dialog if no browser can be opened. (Closes Java auto-provisioning support #6)
  • The button can be more specific and say "Download Java 25" if desired
  • I could also "hyperlink" the "Select Java 21+ Executable" label, but that's less obvious for a confused user to click on than a big "Download Java" button.
• Add a dark mode, default on, configurable
• Pre-select the latest Cleanroom Launcher version
• Specify that we want a Java 21+ executable in the label above the path-to-executable box
• "Hyperlink" the "Java Arguments" part of the "Add Java Arguments:" label to open to the Cleanroom Wiki page on JVM Arguments

[Copilot]

Pull request overview

This PR enhances the Cleanroom Relauncher GUI with user experience improvements including a "Download Java" button, dark mode support, and improved default selections. The button provides direct access to Java downloads via the system browser or displays the download link in a fallback dialog. Dark mode is implemented as a configurable option that defaults to enabled.

• Added "Download Java" button that opens the Adoptium Temurin download page or shows a dialog with the link
• Implemented dark mode functionality with configuration persistence
• Changed default selection to pre-select the latest Cleanroom release instead of using an uninitialized value

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/main/java/com/cleanroommc/relauncher/gui/SupportingFrame.java	Fixed initial visibility to false (prevents supporting frame from appearing)
src/main/java/com/cleanroommc/relauncher/gui/RelauncherGUI.java	Added Download Java button with browser integration, dark mode UI implementation, updated label to specify Java 21+, and fixed release pre-selection
src/main/java/com/cleanroommc/relauncher/config/RelauncherConfiguration.java	Added darkMode configuration field with getter/setter methods
.vscode/settings.json	Added VS Code Java null analysis setting

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[Copilot]

The download URL points to Java 25 (version=25), but the error messages say "Java 21 or later". This creates an inconsistency. Either update the URL to point to Java 21 downloads, or update the error messages to say "Java 25 or later" to match the URL.

Suggested change

	"Please download Java 21 or later from:\n" + downloadUrl,
	"Download Java",
	JOptionPane.INFORMATION_MESSAGE);
	}
	} catch (Exception ex) {
	CleanroomRelauncher.LOGGER.error("Failed to open browser", ex);
	JOptionPane.showMessageDialog(this,
	"Please download Java 21 or later from:\n" + downloadUrl,
	"Please download Java 25 or later from:\n" + downloadUrl,
	"Download Java",
	JOptionPane.INFORMATION_MESSAGE);
	}
	} catch (Exception ex) {
	CleanroomRelauncher.LOGGER.error("Failed to open browser", ex);
	JOptionPane.showMessageDialog(this,
	"Please download Java 25 or later from:\n" + downloadUrl,

[Copilot]

[nitpick] IDE-specific settings files like .vscode/settings.json should typically not be committed to version control as they contain personal editor preferences. Consider adding .vscode/ to .gitignore and removing this file from the repository to avoid conflicts between different developers' IDE configurations.

[trustytrojan]

Note: the dark mode is not fully working on Windows, idk why, probably best to leave it default disabled in config. Do this before merging

[Rongmario]

Superseded by #36, thank you for the work nonetheless.