feat(project-editor): add field-schema registry + test harness

Milestone 1 of the Configuration Engine sprint.

- Add schema/ registry: FieldSchema model, SECTION_FIELD_SCHEMAS covering
  every editable field per section, and EditorSchemaService (getFields,
  getField, all, getByPath). Single source of truth for labels, defaults,
  and validator references; sections stay hand-authored (metadata-augmented).
- Stand up Karma + Jasmine (ng test) with a headless, sandbox-free Chrome
  launcher; add tsconfig.spec.json, karma.conf.js, angular.json test target,
  and npm "test" script. First spec: editor-schema.service.spec (7 passing).

No behavior change. Gate: arch:check, tsc --noEmit, npm test (7/7), build all green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tsconfig.spec.json

@@ -0,0 +1,15 @@
+/* To learn more about Typescript configuration file: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html. */
+/* To learn more about Angular compiler options: https://angular.dev/reference/configs/angular-compiler-options. */
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./out-tsc/spec",
+    "types": [
+      "jasmine"
+    ]
+  },
+  "include": [
+    "src/**/*.spec.ts",
+    "src/**/*.d.ts"
+  ]
+}