fix(collaboration): harden delegated task isolation (#1486)

* feat(collaboration): isolate delegated artifacts and child runs

Isolate delegated inputs and outputs behind secure artifact exchange lifecycles. Scope Agent Link tasks by tenant and root agent, and enforce delegation spawn-tree boundaries. Add process-wide child-run admission and preserve logical media paths across native, MCP, and sandbox execution.

* fix(collaboration): harden delegated task isolation

Enforce tenant and root-agent task scope across migrations and stores. Add exactly-once async completion delivery, delegated sandbox boundaries, and confined artifact and media recovery across runtime surfaces.

* fix(collaboration): recover interrupted async tasks

* fix(collaboration): normalize persisted child-run status

---------

Co-authored-by: ntduc <ntduc@cpp.ai.vn>

tests/integration/sqlite_smoke_test.go

@@ -91,6 +91,7 @@ func TestSQLiteSmokeTest(t *testing.T) {
 		taskID := uuid.Must(uuid.NewV7())
 		task := &store.SubagentTaskData{
 			ParentAgentKey: agentKey,
+			RootAgentID:    agentID,
 			Subject:        "smoke task",
 			Description:    "test",
 			Status:         "running",
@@ -102,7 +103,7 @@ func TestSQLiteSmokeTest(t *testing.T) {
 		if err := stores.SubagentTasks.Create(ctx, task); err != nil {
 			t.Fatalf("Create: %v", err)
 		}
-		got, err := stores.SubagentTasks.Get(ctx, taskID)
+		got, err := stores.SubagentTasks.Get(ctx, agentID, taskID)
 		if err != nil {
 			t.Fatalf("Get: %v", err)
 		}