refactor(@angular/build): make runner optional in unit-test builder

The `runner` option in the `unit-test` builder is now optional to streamline the user configuration.

If the `runner` option is not provided, the builder now defaults to using the `vitest` value.

The builder's schema has been updated to reflect this change by removing `runner` from the required properties and updating its entry to document the new default behavior.

Author: clydin

packages/angular/build/src/builders/unit-test/options.ts

@@ -82,7 +82,7 @@ export async function normalizeOptions(
     include: options.include ?? ['**/*.spec.ts'],
     exclude: options.exclude,
     filter,
-    runnerName: runner,
+    runnerName: runner ?? 'vitest',
     coverage: options.coverage
       ? {
           all: options.coverageAll,

packages/angular/build/src/builders/unit-test/schema.json

@@ -16,6 +16,7 @@
     "runner": {
       "type": "string",
       "description": "Specifies the test runner to use for test execution.",
+      "default": "vitest",
       "enum": ["karma", "vitest"]
     },
     "browsers": {
@@ -267,5 +268,5 @@
     }
   },
   "additionalProperties": false,
-  "required": ["runner"]
+  "required": []
 }