refactor: remove legacy data compatibility

tests/sessions/transcriptStore.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, beforeEach, describe, expect, it } from "bun:test";
-import { mkdtemp, rm, writeFile } from "node:fs/promises";
+import { mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 
@@ -19,63 +19,6 @@ describe("SessionTranscriptStore", () => {
     await rm(tempDir, { force: true, recursive: true });
   });
 
-  it("falls back to legacy runtime-session transcripts by client session id and migrates on append", async () => {
-    await writeFile(
-      join(tempDir, "actor-1__project-1__runtime-session-1.json"),
-      JSON.stringify(
-        {
-          actorKey: "actor-1",
-          clientSessionId: "thread-1",
-          projectKey: "project-1",
-          sessionId: "runtime-session-1",
-          turns: [
-            {
-              id: "turn-1",
-              assistantMessage: "先检查泵站流量。",
-              timestamp: "2026-05-21T00:00:00.000Z",
-              toolCallCount: 1,
-              userMessage: "帮我看一下当前异常。",
-            },
-          ],
-          updatedAt: "2026-05-21T00:00:00.000Z",
-        },
-        null,
-        2,
-      ),
-      "utf8",
-    );
-
-    const recentTurns = await store.getRecentTurns(
-      {
-        actorKey: "actor-1",
-        clientSessionId: "thread-1",
-        projectKey: "project-1",
-        sessionId: "thread-1",
-      },
-      5,
-    );
-
-    expect(recentTurns).toHaveLength(1);
-    expect(recentTurns[0]?.userMessage).toBe("帮我看一下当前异常。");
-
-    const transcript = await store.appendTurn(
-      {
-        actorKey: "actor-1",
-        clientSessionId: "thread-1",
-        projectKey: "project-1",
-        sessionId: "thread-1",
-      },
-      {
-        assistantMessage: "已经定位到 3 条疑似异常支路。",
-        toolCallCount: 2,
-        userMessage: "继续分析这些支路。",
-      },
-    );
-
-    expect(transcript.sessionId).toBe("thread-1");
-    expect(transcript.turns).toHaveLength(2);
-  });
-
   it("clones only the kept prefix when forking a thread", async () => {
     await store.appendTurn(
       {