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>

angular.json

@@ -117,6 +117,32 @@
         },
         "extract-i18n": {
           "builder": "@angular/build:extract-i18n"
+        },
+        "test": {
+          "builder": "@angular/build:karma",
+          "options": {
+            "polyfills": [
+              "zone.js",
+              "zone.js/testing"
+            ],
+            "tsConfig": "tsconfig.spec.json",
+            "karmaConfig": "karma.conf.js",
+            "inlineStyleLanguage": "scss",
+            "assets": [
+              {
+                "glob": "**/*",
+                "input": "public"
+              },
+              {
+                "glob": "**/*",
+                "input": "src/assets",
+                "output": "assets"
+              }
+            ],
+            "styles": [
+              "src/styles.scss"
+            ]
+          }
         }
       }
     }