Tweak history: load up to 500 instead 1000, skip empty chats #5545

Job	Run time
build-and-check	2m 33s
test-integration-packages/internal	1m 4s
test-integration-packages/billing	1m 0s
test-integration-sdk	45s
test-integration-cli	43s
test-integration-packages/agent-runtime	38s
test-integration-common	45s
test-integration-web	39s
test-packages/internal	55s
test-common	40s
test-cli	1m 11s
test-web	50s
test-packages/agent-runtime	58s
test-sdk	51s
test-packages/billing	38s
test-.agents	44s
	14m 54s

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