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

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

internal/agent/loop_pipeline_tool_callbacks.go

@@ -384,6 +384,6 @@ func makeToolEmitRun(l *Loop, req *RunRequest) func(AgentEvent) {
 		event.Channel = req.Channel
 		event.ChatID = req.ChatID
 		event.TenantID = l.tenantID
-		l.emit(event)
+		l.emit(redactDelegationAgentEvent(req, event))
 	}
 }