fix(tracing): make SGP processor stateless to stop dropping span closes #1512

Job	Run time
find-tutorials	5s
test-00_sync/020_streaming	2m 32s
test-00_sync/030_langgraph	3m 10s
test-10_async/00_base/010_multiturn	2m 11s
test-00_sync/000_hello_acp	1m 57s
test-10_async/10_temporal/080_open_ai_agents_sdk_human_in_the_loop	2m 5s
test-10_async/10_temporal/060_open_ai_agents_sdk_hello_world	2m 3s
test-10_async/00_base/080_batch_events	3m 4s
test-10_async/00_base/000_hello_acp	1m 48s
test-10_async/00_base/030_tracing	2m 3s
test-10_async/00_base/040_other_sdks	3m 44s
test-10_async/10_temporal/020_state_machine	2m 23s
test-10_async/10_temporal/070_open_ai_agents_sdk_tools	2m 7s
test-10_async/00_base/100_langgraph	2m 6s
test-10_async/10_temporal/030_custom_activities	2m 36s
test-10_async/00_base/020_streaming	2m 8s
test-10_async/10_temporal/090_claude_agents_sdk_mvp	1m 57s
test-00_sync/010_multiturn	2m 35s
test-10_async/10_temporal/010_agent_chat	2m 43s
test-10_async/10_temporal/000_hello_acp	2m 1s
test-10_async/10_temporal/050_agent_chat_guardrails	2m 0s
Test Summary	7s
	47m 25s

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