fix: prevent duplicate tool_result in subtask delegation (EXT-665) #22140

Job	Run time
check-openrouter-api-key	4s
compile	2m 46s
platform-unit-test (ubuntu-latest)	6m 5s
platform-unit-test (windows-latest)	10m 28s
check-translations	41s
knip	53s
integration-test	3m 6s
	24m 3s

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