fix UI/UX: Mode switch performance from 1 sec -> instant #5949

Job	Run time
check-openrouter-api-key	1s
check-translations	47s
compile	1m 18s
knip	50s
test-extension (ubuntu-latest)	2m 0s
test-webview (ubuntu-latest)	1m 27s
test-extension (windows-latest)	2m 47s
test-webview (windows-latest)	3m 28s
integration-test	0s
unit-test	1s
	12m 39s

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