fix(themes): match IntelliJ's gutter, selected tab border and completion colours on import (#1424)

Themes imported from IntelliJ drew a lighter gutter strip and kept the built-in blue for the selected tab's border and completion matches. The converter read the classic UI's GUTTER_BACKGROUND, where the new UI paints EDITOR_GUTTER_BACKGROUND or else the editor's background; it read EditorTabs.underlineColor, where Islands borders the selected tab with underlinedBorderColor; and it didn't map CompletionPopup.matchForeground. Scheme attributes written as `<value />` (no colours, not inherited) now show as plain text instead of keeping the built-in colours.

Co-authored-by: ldg030201 <[email protected]>

scripts/theme/theme.test.ts

@@ -91,6 +91,8 @@ describe("IntelliJ theme import", () => {
       "Button": { "default": { "startBackground": "accent" } },
       "Popup.background": "#181f28",
       "Label.infoForeground": "#80888F80",
+      "EditorTabs": { "underlineColor": "#405060", "underlinedBorderColor": "#bd93f9" },
+      "CompletionPopup.matchForeground": "#ff79c6",
       "Tree": { "rowHeight": 24 }
     }
   }`;
@@ -99,6 +101,7 @@ describe("IntelliJ theme import", () => {
     <option name="CARET_COLOR" value="ffcc00" />
     <option name="LINE_NUMBERS_COLOR" value="0" />
     <option name="UNKNOWN_KEY" value="123456" />
+    <option name="GUTTER_BACKGROUND" value="313335" />
   </colors>
   <attributes>
     <option name="DEFAULT_KEYWORD">
@@ -126,6 +129,9 @@ describe("IntelliJ theme import", () => {
       </value>
     </option>
     <option name="DEFAULT_CONSTANT" baseAttributes="DEFAULT_IDENTIFIER" />
+    <option name="DEFAULT_INSTANCE_FIELD">
+      <value />
+    </option>
   </attributes>
 </scheme>`;
 
@@ -138,6 +144,9 @@ describe("IntelliJ theme import", () => {
     expect(t.tokens["--bg-selected"]).toBe("#203040");
     expect(t.tokens["--fg-muted"]).toBe("#80888f80");
     expect(t.tokens["--fg"]).toBe("#c0c8d0");
+    // Islands borders the selected tab with underlinedBorderColor.
+    expect(t.tokens["--border-tab-selected"]).toBe("#bd93f9");
+    expect(t.tokens["--fg-completion-match"]).toBe("#ff79c6");
     expect(s).toBeNull();
   });
 
@@ -165,9 +174,12 @@ describe("IntelliJ theme import", () => {
       "--syn-comment-style": "italic",
       "--fg-editor": "#a9b7c6",
       "--bg-editor": "#2b2b2b",
+      // GUTTER_BACKGROUND is the classic UI's: the gutter keeps the editor's background.
       "--bg-editor-gutter": "#2b2b2b",
       "--wave-error": "#ff0000",
       "--editor-error-decoration": "underline wavy #ff0000",
+      // <value />: plain text, not the parent scheme's colour.
+      "--syn-property": "#a9b7c6",
     });
     expect(s.tokens["--syn-constant"]).toBeUndefined();
   });