fix: render registry workspaces for harness

backend/test/routes-sessions.test.ts

@@ -601,6 +601,8 @@ test("session lifecycle locates a B session when installation default is A", asy
     provider: "zai", model: "glm-5.2", thinking: "low",
   };
   const calls: string[] = [];
+  const runtimeSources: string[] = [];
+  const runtimeOptions: string[] = [];
   let active: any;
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {
@@ -622,11 +624,21 @@ test("session lifecycle locates a B session when installation default is A", asy
         calls.push(`reopen:${workspace}`);
         expect(id).toBe("session-b");
       },
+      acquireWorkspaceRuntime: (workspace: string) => {
+        runtimeSources.push(workspace);
+        return {
+          path: `/runtime/${runtimeSources.length}.yaml`,
+          workspaceId: "b-workspace",
+          workspaceRevision: "c".repeat(40),
+          release: vi.fn(),
+        };
+      },
     } as any,
     readiness: { ensure: async () => ({ ok: true }) } as any,
     mgr: {
       get: () => active,
-      createFor: () => {
+      createFor: (_id: string, options: any) => {
+        runtimeOptions.push(options.runtimeConfig?.path ?? "missing");
         active = { bridge: { onClientEvent: () => {}, respond: () => true, turnState: () => "idle" } };
         return active;
       },
@@ -673,6 +685,8 @@ test("session lifecycle locates a B session when installation default is A", asy
   expect(calls).toContain(`list:${bPath}`);
   expect(calls).toContain(`show:${bPath}`);
   expect(calls).toContain(`reopen:${bPinnedPath}`);
+  expect(runtimeSources).toEqual([bPath, bPinnedPath]);
+  expect(runtimeOptions).toEqual(["/runtime/1.yaml", "/runtime/2.yaml"]);
 });
 
 test("POST /sessions usa i settings (workspace/provider/model/thinking) e crea+avvia", async () => {