perf: optimize Java tracing agent (E2E reduction + serialization + writes) #84

Job	Run time
determine-changes	10s
prek	20s
type-check	28s
e2e-java (java-void-optimization-nogit, end_to_end_test_java_void_optimization.py, 70, true)	2m 9s
e2e-java (java-fibonacci-nogit, end_to_end_test_java_fibonacci.py, 70, true)	2m 8s
e2e-java (java-tracer, end_to_end_test_java_tracer.py, 10)	2m 9s
unit-tests (ubuntu-latest, 3.14)	2m 9s
unit-tests (ubuntu-latest, 3.10)	2m 7s
unit-tests (windows-latest, 3.13)	2m 16s
unit-tests (ubuntu-latest, 3.13)	2m 9s
unit-tests (ubuntu-latest, 3.12)	2m 8s
unit-tests (ubuntu-latest, 3.11)	2m 8s
e2e-python (bubble-sort-pytest-nogit, end_to_end_test_bubblesort_pytest.py, 70, true)	2m 8s
e2e-python (bubble-sort-unittest, end_to_end_test_bubblesort_unittest.py, 40)	2m 9s
e2e-python (tracer-replay, end_to_end_test_tracer_replay.py, 10)	2m 8s
e2e-python (benchmark-bubble-sort, end_to_end_test_benchmark_sort.py, 5)	2m 9s
e2e-python (futurehouse-structure, end_to_end_test_futurehouse.py, 5)	2m 9s
e2e-python (init-optimization, end_to_end_test_init_optimization.py, 10)	2m 10s
e2e-python (async-optimization, end_to_end_test_async.py, 10)	2m 10s
e2e-python (topological-sort, end_to_end_test_topological_sort_worktree.py, 5)	2m 9s
e2e-python (coverage-e2e, end_to_end_test_coverage.py, black)	2m 10s
unit-tests (ubuntu-latest, 3.9)	2m 8s
e2e-js	0s
required checks passed	3s
	41m 54s

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