Add workspace management methods

[Olbrasoft]

Summary

This PR adds five new D-Bus methods for workspace management:

• GetWorkspaces: Returns JSON array of all workspaces with index, active status, and window count
• GetActiveWorkspace: Returns the index of the active workspace
• GetWorkspaceCount: Returns the total number of workspaces
• SwitchWorkspace: Switches to a specific workspace by index
• GetWorkspaceWindows: Returns windows on a specific workspace

Use Case

These methods enable programmatic workspace control for automation tools and custom desktop management applications. For example:

• Desktop automation scripts that need to manage windows across workspaces
• Virtual assistant applications that can switch workspaces or query workspace state
• Custom desktop panels that show workspace information

Example Usage

# Get all workspaces
gdbus call --session --dest org.gnome.Shell \
  --object-path /org/gnome/Shell/Extensions/Windows \
  --method org.gnome.Shell.Extensions.Windows.GetWorkspaces

# Get active workspace index
gdbus call --session --dest org.gnome.Shell \
  --object-path /org/gnome/Shell/Extensions/Windows \
  --method org.gnome.Shell.Extensions.Windows.GetActiveWorkspace

# Switch to workspace 1
gdbus call --session --dest org.gnome.Shell \
  --object-path /org/gnome/Shell/Extensions/Windows \
  --method org.gnome.Shell.Extensions.Windows.SwitchWorkspace 1

Test Plan

• Test GetWorkspaces returns correct workspace count and active status
• Test GetActiveWorkspace returns correct index
• Test GetWorkspaceCount returns correct count
• Test SwitchWorkspace changes to correct workspace
• Test GetWorkspaceWindows returns windows on specified workspace
• Test error handling for invalid workspace index

[toupeira]

Was just looking for a way to do this and found this PR, thanks @Olbrasoft! 🙇

I tested on GNOME 49.2, seems to work great.