fix(init): make shallow init adapt to existing memory structure [LET-7995] (#1417)

src/tests/cli/init-background-subagent.test.ts

@@ -77,7 +77,8 @@ describe("init wiring", () => {
     memoryDir: "/tmp/test/.memory",
     gitContext: "- branch: main\n- status: (clean)",
     gitIdentity: "Test User <test@example.com>",
-    existingMemory: "(empty)",
+    existingMemoryPaths: [] as string[],
+    existingMemory: "",
     dirListing: "README.md\npackage.json\nsrc",
   };