Issue/2740 code quality refactors

[theaniketgiri]

Part of #2740

This PR addresses the "Match statements" section of the tracking issue by extracting three large match arms from process_message() into dedicated helper methods.

Changes

Extracted the following helper methods in DocumentMessageHandler:

Method	Lines Extracted	Purpose
handle_group_selected_layers	~50 lines	Handles layer grouping in both artboard and non-artboard workflows
handle_move_selected_layers_to	~85 lines	Handles layer movement with proper transform preservation
handle_nudge_selected_layers	~75 lines	Handles keyboard nudging with optional resize mode

Benefits

• Improved readability: The main match statement is now ~210 lines shorter
• Better maintainability: Each operation is now self-contained in its own method
• Easier testing: Helper methods can potentially be unit tested independently
• Clearer intent: Method names describe what the code does

Before/After

Before:

DocumentMessage::GroupSelectedLayers { group_folder_type } => {
    // ~50 lines of inline code
}

After:

DocumentMessage::GroupSelectedLayers { group_folder_type } => {
    self.handle_group_selected_layers(group_folder_type, responses);
}

Testing

• Verified compilation with cargo check
• Logic and behavior remain unchanged - this is a pure refactor
• Existing tests pass (note: SIGSEGV in tests is a pre-existing issue on master)

---

[timon-schelling]

Why the new workflow? That seems unrelated.

Converted to draft because this not ready for review.

[theaniketgiri]

Why the new workflow? That seems unrelated.

Converted to draft because this not ready for review.

Hi @timon-schelling, thanks for the review!

You're absolutely right - both the workflow file and pnpm-lock were accidentally included. They were from a different branch I was working on and got mixed in when I created this PR.

I've fixed this now:

Rebased onto master
Removed the unrelated workflow file and pnpm-lock
The PR now only contains the refactoring changes