Address review findings on the #2923 fail-closed parse fix:
- Comment-only files produce ValueExpected with no JSON value; treat that
as empty config instead of INVALID_JSONC. Partial object trees still throw.
- readConfigLayers no longer lets one unparseable layer abort valid sibling
layers. Mutations still fail closed on the custom/user write target.
Co-authored-by: serkraser <serkraser@gmail.com>
jsonc-parser was returning truncated trees (often only `$schema`) when
configs contained JSON5-style unquoted keys. Config mutations then backed
up and overwrote the full file with that stub. Check parse errors on read
and refuse to overwrite unparseable files on write in web and VS Code.
Fixes#2923
Co-authored-by: serkraser <serkraser@gmail.com>
