v1.9.3 — Custom checkbox CSS (indeterminate rendering fix)

Fixed

• Indeterminate checkbox mark washed out / invisible — replaced the browser's native checkbox rendering (accent-color) with a fully custom CSS implementation (appearance: none + ::after pseudo-elements); all three states (unchecked / checked / indeterminate) now render consistently: empty border when unchecked, solid --vscode-button-background fill when checked or partially selected, white checkmark or white dash on top