This stopped being an issue for me with a recent package update, so I guess Qt6 was fixed upstream?

There were three distinct mechanisms for signaling symbol changes in DolphinQt: `Host::NotifyMapLoaded`, `MenuBar::NotifySymbolsUpdated`, and `CodeViewWidget::SymbolsChanged`. The behavior of these signals has been consolidated into the new `Host::PPCSymbolsUpdated` signal, which can be emitted from anywhere in DolphinQt to properly update symbols everywhere in DolphinQt.

Window icon was missing from QDialog lacking a parent.
Giving the QDialog a parent revealed I had failed to make it properly non-modal, necessitating further changes.
Settings save less often, now only upon destruction.
Construction of BranchWatchDialog is now deferred.

BranchWatchDialog: A Total Replacement for CodeDiffDialog

With a purpose-built Branch Watch feature built into the emulated system: BranchWatchDialog, replacing CodeDiffDialog, is now better than ever!

The CPU thread guard already allows access to the system instance. We can
remove the system parameter to reduce rendundancy here.