[red-knot] Fix offset handling in playground for 2-code-point UTF16 c… #25

Job	Run time
cargo fmt	21s
Determine changes	11s
mkdocs	4m 31s
cargo build (release)	7m 36s
pre-commit	1s
python package	2m 52s
cargo test (linux)	1d 0h 0m 0s
cargo clippy	4m 5s
cargo test (windows)	1s
cargo test (linux, release)	1s
cargo test (wasm)	2m 57s
benchmarks	0s
cargo shear	29s
formatter instabilities and black similarity	5m 2s
test scripts	2m 50s
cargo fuzz build	6m 34s
cargo build (msrv)	1s
check playground	0s
ecosystem	-1s
test ruff-lsp	-1s
fuzz parser	-1s
	1d 0h 37m 29s

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