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>

src/main/database/migrations/059-task-handoff.ts

@@ -0,0 +1,6 @@
+export const taskHandoffSchema = `
+  alter table tasks add column handoff_json text;
+
+  insert into schema_migrations(version, name, applied_at)
+  values (59, 'task_handoff', datetime('now'));
+`;

src/main/database/schema.ts

@@ -57,6 +57,7 @@ import { taskOriginSchema } from "./migrations/055-task-origin";
 import { kimiProvidersSchema } from "./migrations/056-kimi-providers";
 import { kimiCodeProviderSchema } from "./migrations/057-kimi-code-provider";
 import { integrationKeysSchema } from "./migrations/058-integration-keys";
+import { taskHandoffSchema } from "./migrations/059-task-handoff";
 
 interface Migration {
   version: number;
@@ -123,6 +124,7 @@ const MIGRATIONS: Migration[] = [
   { version: 56, name: "kimi_providers", sql: kimiProvidersSchema },
   { version: 57, name: "kimi_code_provider", sql: kimiCodeProviderSchema },
   { version: 58, name: "integration_keys", sql: integrationKeysSchema },
+  { version: 59, name: "task_handoff", sql: taskHandoffSchema },
 ];
 
 const SCHEMA_VERSION = MIGRATIONS[MIGRATIONS.length - 1].version;