更新memory读取机制，新增前需要先list阅读已有的内容

tests/memory/store.test.ts

@@ -37,7 +37,7 @@ describe("MemoryStore", () => {
     expect(second.detail).toBe("memory already existed");
   });
 
-  it("rejects rewritten memories that are too similar to an existing one", async () => {
+  it("allows rewritten memories when the content is not exactly the same", async () => {
     await store.upsert("workspace", "project-1", {
       content: "保存记忆前先查看当前 workspace memory，避免重复写入相同约束。",
       source: "tool",
@@ -48,12 +48,12 @@ describe("MemoryStore", () => {
       source: "tool",
     });
 
-    expect(result.changed).toBe(false);
-    expect(result.detail).toBe("similar memory already exists");
-    expect(result.entry?.content).toBe("保存记忆前先查看当前 workspace memory，避免重复写入相同约束。");
+    expect(result.changed).toBe(true);
+    expect(result.detail).toBe("memory stored");
+    expect(result.entry?.content).toBe("写入前先看一遍当前 workspace 记忆，避免把同样的约束重复保存进去。");
   });
 
-  it("rejects replace when the new content overlaps a similar existing memory", async () => {
+  it("rejects replace when the new content would become an exact duplicate", async () => {
     const first = await store.upsert("user", "actor-1", {
       content: "回答时默认使用中文，并保持结论先行。",
       source: "tool",
@@ -64,13 +64,13 @@ describe("MemoryStore", () => {
     });
 
     const result = await store.replace("user", "actor-1", second.entry?.id ?? "", {
-      content: "默认使用中文回答，结论放在最前面。",
+      content: "回答时默认使用中文，并保持结论先行。",
       source: "tool",
     });
 
     expect(first.changed).toBe(true);
     expect(second.changed).toBe(true);
     expect(result.changed).toBe(false);
-    expect(result.detail).toBe("replacement would overlap with a similar existing memory");
+    expect(result.detail).toBe("replacement would duplicate an existing memory");
   });
 });