Remove tool from context-pruner so it doesn't add a user prompt message. #4109

Job	Run time
build-and-check	2m 40s
test-integration-.agents	41s
test-integration-common	38s
test-integration-backend	1m 8s
test-integration-web	41s
test-.agents	49s
test-integration-cli	45s
test-common	1m 29s
test-backend	1m 32s
test-integration-packages/agent-runtime	46s
test-npm-app	44s
test-cli	1m 32s
test-packages/agent-runtime	1m 32s
test-web	1m 32s
test-integration-npm-app	41s
	17m 10s

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