refactor(@schematics/angular): support parsing plain template literals in karma config analyzer

Updates the AST analyzer to accept static backtick strings that do not contain runtime expressions. Previously, even simple template literals resulted in a fallback warning flag, triggering manual migration overrides unnecessarily.

Author: clydin

packages/schematics/angular/migrations/migrate-karma-to-vitest/karma-config-analyzer.ts

@@ -80,7 +80,8 @@ export function analyzeKarmaConfig(content: string): KarmaConfigAnalysis {
   function extractValue(node: ts.Expression): KarmaConfigValue {
     switch (node.kind) {
       case ts.SyntaxKind.StringLiteral:
-        return (node as ts.StringLiteral).text;
+      case ts.SyntaxKind.NoSubstitutionTemplateLiteral:
+        return (node as ts.StringLiteral | ts.NoSubstitutionTemplateLiteral).text;
       case ts.SyntaxKind.NumericLiteral:
         return Number((node as ts.NumericLiteral).text);
       case ts.SyntaxKind.TrueKeyword:

packages/schematics/angular/migrations/migrate-karma-to-vitest/karma-config-analyzer_spec.ts

@@ -293,4 +293,33 @@ describe('Karma Config Analyzer', () => {
     expect(settings.size).toBe(0);
     expect(hasUnsupportedValues).toBe(true);
   });
+
+  it('should parse plain template literal strings without substitution', () => {
+    const karmaConf = `
+      module.exports = function (config) {
+        config.set({
+          basePath: \`some/path\`,
+        });
+      };
+    `;
+    const { settings, hasUnsupportedValues } = analyzeKarmaConfig(karmaConf);
+
+    expect(settings.get('basePath') as unknown).toBe('some/path');
+    expect(hasUnsupportedValues).toBe(false);
+  });
+
+  it('should flag template literals with substitution as unsupported', () => {
+    const karmaConf = `
+      const relativePath = './coverage';
+      module.exports = function (config) {
+        config.set({
+          basePath: \`\${relativePath}/test\`,
+        });
+      };
+    `;
+    const { settings, hasUnsupportedValues } = analyzeKarmaConfig(karmaConf);
+
+    expect(settings.has('basePath')).toBe(false);
+    expect(hasUnsupportedValues).toBe(true);
+  });
 });