feat: establish unified administration and model context baseline

backend/test/routes-sql-meta.test.ts

@@ -160,8 +160,7 @@ test("GET /models returns session choices from the installation model catalog",
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {} as any,
     runtimeModelCatalog: {
-      defaultSession: "zai/glm-5.2",
-      defaultMetadataGeneration: null,
+      defaultInteraction: "zai/glm-5.2",
       embedding: { id: "ollama/qwen3-embedding:0.6b", dimensions: 1024 },
       sessionModels: () => [{
         id: "zai/glm-5.2", provider: "zai", model: "glm-5.2", label: "GLM 5.2",
@@ -187,8 +186,7 @@ test("GET /models returns an empty list when the catalog has no session models",
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {} as any,
     runtimeModelCatalog: {
-      defaultSession: null,
-      defaultMetadataGeneration: null,
+      defaultInteraction: null,
       embedding: null,
       sessionModels: () => [],
       metadataModels: () => [],