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>

karma.conf.js

@@ -0,0 +1,26 @@
+// Karma configuration for `ng test` (@angular/build:karma builder).
+// A headless, sandbox-free Chrome launcher so the suite runs in CI and in
+// restricted/dev environments where Chrome isn't on PATH. CHROME_BIN falls
+// back to the default Windows install path when the env var isn't set.
+process.env.CHROME_BIN =
+  process.env.CHROME_BIN || 'C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe';
+
+module.exports = function (config) {
+  config.set({
+    frameworks: ['jasmine'],
+    plugins: [
+      require('karma-jasmine'),
+      require('karma-chrome-launcher'),
+      require('karma-jasmine-html-reporter'),
+    ],
+    browsers: ['ChromeHeadlessNoSandbox'],
+    customLaunchers: {
+      ChromeHeadlessNoSandbox: {
+        base: 'ChromeHeadless',
+        flags: ['--no-sandbox', '--disable-gpu', '--disable-dev-shm-usage'],
+      },
+    },
+    reporters: ['progress'],
+    restartOnFileChange: true,
+  });
+};