Diff pane ignores custom theme colors (hardcoded Tailwind CSS variables) #3567

Description

When using a custom theme with editor.colors.addition / editor.colors.deletion / editor.colors.modified configured, the diff pane (v2 WorkspaceDiff) ignores these theme values and uses hardcoded Tailwind CSS variables instead.

Root Cause

In WorkspaceDiff.tsx (lines ~70-86), gitDecorationColors hardcodes Tailwind CSS variables:

const gitDecorationColors =
    activeTheme.type === "dark"
        ? {
            addition: "var(--color-green-400)",
            deletion: "var(--color-red-500)",
            modified: "var(--color-yellow-400)",
          }
        : { ... };
const themeVars = {
    ...baseThemeVars,
    "--diffs-addition-color-override": gitDecorationColors.addition,
    "--diffs-deletion-color-override": gitDecorationColors.deletion,
    "--diffs-modified-color-override": gitDecorationColors.modified,
};

This overwrites baseThemeVars which correctly derives from getEditorTheme(theme) → getDiffViewerStyle(), making the theme's editor.colors settings ineffective for the diff view.

Expected Behavior

Diff colors should respect the custom theme's editor.colors.addition, editor.colors.deletion, and editor.colors.modified values. The getDiffViewerStyle() already correctly reads from the theme — removing the hardcoded override in WorkspaceDiff.tsx should fix this.

Steps to Reproduce

1. Create a custom theme JSON with editor.colors section including addition, deletion, modified
2. Import and activate the theme in Settings → Appearance
3. Open the Changes tab to view a diff
4. Observe that diff colors remain the default Tailwind green/red/yellow regardless of theme settings

Environment

• Superset Desktop (macOS)
• Custom theme with both terminal and editor sections defined