fix(ui): smart resolution + existence-validation for code-file paths #1032

Job	Run time
test	41s
build	1m 18s
smoke-binaries (windows-latest, plannotator-win32-x64.exe)	47s
install-script-smoke (ubuntu-latest, plannotator-linux-x64)	22s
smoke-binaries (ubuntu-latest, plannotator-linux-x64)	20s
npm-publish	1m 0s
attest	-1s
release	0s
	4m 27s

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