Show OS console messages in muted grey and add a setting to hide them

When an Objo app runs from Studio, lines the operating system or the app host writes to the app's output stream (for example macOS input-method framework messages such as error messaging the mach port for IMKCFRunLoopWakeUpReliable, which appears when switching keyboard input sources) currently appear in the console output pane in the same red colour as genuine errors. Users reasonably mistake these OS-origin lines for Objo errors even though their app is unaffected.

Studio should:

• Render operating-system and app-host messages in the console output pane in a muted grey colour instead of red, so they are visually distinct from real errors.
• Add a Show OS messages setting (Settings → Editor, default on). When on, OS messages appear in muted grey; when off, they are not shown at all.