fix(@angular/cli): preserve exact version in ng add when requested

The `ng add` command would previously always add a caret (`^`) prefix
to the resolved package version, even if the user explicitly requested
an exact version. This change ensures that the exact version is preserved
in the package identifier if requested, while maintaining the caret
prefix for general requests to ensure consistent behavior with package
managers.

Author: clydin

packages/angular/cli/src/commands/add/cli.ts

@@ -511,11 +511,12 @@ export default class AddCommandModule
     // Avoid fully resolving the package version from the registry again in later steps
     if (context.packageIdentifier.registry) {
       assert(context.packageIdentifier.name, 'Registry package identifier must have a name');
+      const isExactVersion = context.packageIdentifier.type === 'version';
       context.packageIdentifier = npa.resolve(
         context.packageIdentifier.name,
         // `save-prefix` option is ignored by some package managers so the caret is needed to ensure
         // that the value in the project package.json is correct.
-        '^' + manifest.version,
+        (isExactVersion ? '' : '^') + manifest.version,
       );
     }