Fix SIGABRT crash on macOS 26: dispatch toggleMenuIconDisabled to main queue

[agentheath]

What

Wraps the background-thread call to toggleMenuIconDisabled in dispatch_async(dispatch_get_main_queue(), ...) in pollPB:.

Why

pollPB: dispatches pasteboard reads to a background GCD queue to avoid blocking the main thread while waiting for large clipboard transfers (this is intentional — see the comment in the code). Inside that block, toggleMenuIconDisabled was being called directly from the background thread to restore the menu icon after a Remote Desktop Connection transfer completes.

toggleMenuIconDisabled modifies NSStatusItem via setImage: and setTitle:, which internally update an NSImageView. macOS 26 now enforces stricter main-thread assertions for NSImageView operations (via _NSAsynchronousPreparation), causing an abort trap / SIGABRT.

Fix

// BEFORE
if (largeCopyRisk)
    [self toggleMenuIconDisabled];

// AFTER
if (largeCopyRisk) {
    dispatch_async(dispatch_get_main_queue(), ^{
        [self toggleMenuIconDisabled];
    });
}

The first call to toggleMenuIconDisabled at line 883 (before the dispatch block) is already on the main thread and does not need wrapping.

Scope

Only AppController.m is changed. BezelWindow.m was audited — setSourceIcon: and related image methods are only reachable from main-thread code paths and do not need changes.