assistant2: Factor out `ActiveThread` view (#21555) #961

Job	Run time
Check formatting and Clippy lints	2m 7s
Run tests	7m 8s
Create a Linux *.tar.gz bundle for x86	12m 34s
Create a Linux *.tar.gz bundle for ARM	22m 2s
Create a macOS bundle	27m 28s
Update nightly tag	16s
	1h 11m 35s

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