Q3: record a structured handoff on every delegated task

create_task now pins upstream files by content hash and carries the
source task, source thread, verified facts, open questions and
acceptance criteria into the assignee's prompt.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/execution-modes.test.ts

@@ -53,7 +53,7 @@ function harness(mode: "ai_ceo" | "ai_cofounder"): Harness {
       orgId,
       agent: { id: ceoId, modelProviderId: null, modelId: null },
       taskProjectId: null,
-      taskGoalId: null,
+      taskGoalId: null, taskId: null, sourceThreadId: null,
       workspace: { id: workspaceId, localPath: workspaceRoot, writeAccess: true },
     },
     deps: { db: connection.db, organization, chat: new ChatService(connection.db) },