fix: update test results bar UI and rename autofix tab

Rename "AI Hints" tab to "Custom Hints" to improve clarity and better
reflect its purpose. Remove unnecessary gap between panes when expanded
to create a cleaner layout. Add left padding to the right pane when
visible to improve spacing and visual balance. These changes enhance
usability and visual consistency of the test results bar component.

Author: rohitpaulk

app/components/course-page/test-results-bar/index.hbs

@@ -24,7 +24,7 @@
   >
     {{#if this.isExpanded}}
       {{! min-h-0 ensures div doesn't outgrow container !}}
-      <div class="flex gap-6 grow border-b border-gray-800 px-6 min-h-0">
+      <div class="flex grow border-b border-gray-800 px-6 min-h-0">
         <CoursePage::TestResultsBar::Pane
           @activeTabSlug={{this.activeTabSlugForLeftPane}}
           @onActiveTabSlugChange={{fn (mut this.activeTabSlugForLeftPane)}}
@@ -50,7 +50,7 @@
           @activeTabSlug={{this.activeTabSlugForRightPane}}
           @onActiveTabSlugChange={{fn (mut this.activeTabSlugForRightPane)}}
           @availableTabSlugs={{this.availableTabSlugsForRightPane}}
-          class="transition-[width,opacity] duration-200 ease-out {{if this.shouldShowRightPane 'w-1/2 opacity-100' 'w-[0] opacity-0'}} grow"
+          class="transition-[width,opacity] duration-200 ease-out {{if this.shouldShowRightPane 'w-1/2 pl-6 opacity-100' 'w-[0] opacity-0'}} grow"
         >
           {{! Extra if convinces glint that autofixRequest is not null }}
           {{#if this.autofixRequestForActiveStep}}

app/components/course-page/test-results-bar/pane.ts

@@ -25,7 +25,7 @@ export default class Pane extends Component<Signature> {
       },
       {
         slug: 'autofix',
-        title: 'AI Hints',
+        title: 'Custom Hints',
         icon: 'sparkles',
       },
     ];