#2278: Split main-view.fxml into separate layout components

[krystynaShatkovska]

This PR fixes #2278

Implemented changes:

Split main-view.fxml (~300 lines) into three FXML files using fx:include tags:

• navigation.fxml — left sidebar (logo + project/workspace/language selectors)
• status-bar.fxml — bottom status bar (label + progress bar)
• main-view.fxml — shell that includes the two components via fx:include, keeping the center IDE rows inline (their onAction handlers require the parent's controller)

Controller integration:

• App.java / AppBaseTest.java: Replaced setController() with setControllerFactory(type -> controller) so child FXMLs with fx:controller share the same MainController instance
• MainController.java: Added idempotent guard to initialize() so it runs only once across all FXML files

All fx:id references and onAction handlers preserved and verified.

Testing instructions

Build the project with mvn clean test and verify all tests pass
Launch the IDEasy GUI and confirm the main window renders correctly with all three regions (sidebar, center IDE rows, bottom status bar)
Interact with each region to verify functionality is unchanged:

• Open a project and workspace via the sidebar selectors
• Click "Open" buttons for each IDE row
• Trigger a status update in the bottom bar to confirm the label/progress bar work

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Checklist for this PR

Make sure everything is checked before merging this PR. For further info please also see
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• When running mvn clean test locally all tests pass and build is successful
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[coveralls]

Coverage Report for CI Build 32148089094

Coverage decreased (-0.01%) to 72.92%

Details

• Coverage decreased (-0.01%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 34 coverage regressions across 3 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

34 previously-covered lines in 3 files lost coverage.

File	Lines Losing Coverage	Coverage
com/devonfw/ide/gui/MainController.java	29	68.75%
com/devonfw/ide/gui/App.java	4	0.0%
com/devonfw/tools/ide/version/VersionSegment.java	1	90.03%

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Coverage Stats

Relevant Lines:	17560
Covered Lines:	13356
Line Coverage:	76.06%
Relevant Branches:	7761
Covered Branches:	5108
Branch Coverage:	65.82%
Branches in Coverage %:	Yes
Coverage Strength:	3.23 hits per line

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💛 - Coveralls

[laim2003]

Thanks for your PR! Looks good! Sadly I hoped that JavaFX allows for an easier way to fragment layouts without having to add extra checks, but it seems like JavaFX is not very flexible. From what I could research, using a controller factory seems to be the most common way to implement this. Maybe we should rethink the way we will fragment the UI in the future. For now this is good in my opinion.

[hohwille]

@krystynaShatkovska thank your very much for your PR. We should always follow SoC and this is a great improvement for modularity and maintainability of the UI code. Great jib!👍
I left some remark about some code duplication in the test.
However, this should not prevent the merge that I want to get done.
Therefore, I will resolve the comment and merge this PR as is.
It would be great if you can take up the comment and create a new issue from it so it does not get lost.