Unit tests for shell substitution are flaky in windows

[lazysegtree]

Creating this issue to track the fix for unit test failures which utilizes the prompt shell substitution feature

Namely these tests are flaky, in windows

• src/internal/ui/prompt/tokenize_test.go -> Test_resolveShellSubstitution
• src/internal/model_prompt_test.go -> TestModel_Update_Prompt ("open Panel" test)