fix: default PS1 and PS2 in interactive mode (#390) #941

Job	Run time
Build (x86_64/linux)	1m 59s
Source code checks (stable)	29s
Build (aarch64/macos)	1m 51s
Source code checks (1.75.0)	27s
Build (aarch64/linux)	2m 1s
Build (wasm32/wasi-0.2)	1m 8s
Check for unneeded dependencies	1m 2s
Build (x86_64/windows)	2m 4s
Test (linux/x86_64)	1m 52s
Test (macOS)	1m 26s
Benchmarks	0s
External tests / bash-completion test suite	8m 35s
OS target tests (Fedora/latest)	23s
OS target tests (Debian/testing)	16s
OS target tests (Arch Linux/latest)	18s
	23m 51s

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