feat(hub): 结构化运行历史(A-3) + lock 心跳(A-5)

A-3 结构化历史:
- 新增 AgentMessage 表(每条消息的 queryable 投影,transcript 文件仍是 agent 读回记忆)
- 新增 AgentFileChange 表(run 期间文件变更 before/after hash + operation)
- runner.ts: generateText 后 persistAgentMessages 落库 result.responseMessages
- workspace.ts writeFileTool: 写前算 beforeHash(SHA-256),写后算 afterHash,通过 ctx.onFileChange sink 记录
- runner.ts flushFileChanges: 收集 sink 的变更批量写入 AgentFileChange
- ToolContext 加 onFileChange sink 字段
- trigger.ts 接线 runId/sessionId/prisma 到 RunRequest

A-5 lock 心跳:
- ProjectAgentLock 加 heartbeatAt 列
- runner.ts onStepFinish 回调:每步 model step 后更新 heartbeatAt(吞错,lock 可能被 force-release)

60 tests 全过(tsc 干净)。

hub/src/agent/tools.ts

@@ -24,6 +24,11 @@ export interface ToolContext {
   readonly boundChatId: string;
   /** Absolute path to the project's curriculum engineering-file workspace. */
   readonly workspaceDir: string;
+  /** Optional sink for file-change capture (A-3). The writeFile tool calls
+   *  this with before/after hash when it modifies a file; the runner injects
+   *  a collector that flushes to AgentFileChange at run end. Undefined when
+   *  the runner doesn't wire capture (e.g. unit tests). */
+  readonly onFileChange?: (change: { path: string; operation: "CREATE" | "UPDATE" | "DELETE" | "RENAME"; beforeHash: string | null; afterHash: string | null; diff: string | null }) => void;
 }
 
 export type ToolDefinition = Tool;