Improve external display handling and target selection performance #5375

Job	Run time
Format (Cargo)	13s
Lint (Biome)	15s
Typecheck	1m 23s
Format (Biome)	12s
Detect Changes	8s
Clippy (x86_64-pc-windows-msvc, windows-latest)	5m 33s
Clippy (aarch64-apple-darwin, macos-latest)	2m 13s
Verify Tauri plugin versions	-1s
Build Desktop	-1s
Rust cache	-1s
	9m 54s

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