fix(langgraph): Fix behavior around array return values from nodes #2078

Job	Run time
Build	1m 50s
check-readmes-synced	3s
Check formatting	1m 20s
Check linting	1m 45s
Unit Tests (ubuntu-latest, 18.x)	1m 32s
Validate Deno and Node dependencies in sync	8s
Unit Tests (ubuntu-latest, 20.x)	1m 32s
validate-new-notebooks	9s
Unit Tests (ubuntu-latest, 22.4.1)	2m 13s
Unit Tests (windows-latest, 22.4.1)	4m 3s
Unit Tests (macos-latest, 22.4.1)	1m 39s
	16m 14s

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