Initial benchmark implementation

.env

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+# Benchmark universe and derived scenario sizes.
+MAX_VALUE=100000000
+SPARSE_SET_PERCENT=0.004
+SEMI_SPARSE_SET_PERCENT=0.04
+NORMAL_SET_PERCENT=0.4
+DENSE_SET_PERCENT=4
+
+# Requested overlap percentages for the smaller set.
+LOW_OVERLAP_PERCENT=10
+MEDIUM_OVERLAP_PERCENT=50
+HIGH_OVERLAP_PERCENT=80
+
+# Select which density scenarios are included.
+ENABLE_SPARSE_SCENARIO=true
+ENABLE_SEMI_SPARSE_SCENARIO=true
+ENABLE_NORMAL_SCENARIO=true
+ENABLE_DENSE_SCENARIO=true
+
+# Select which overlap scenarios are included.
+ENABLE_LOW_OVERLAP=false
+ENABLE_MEDIUM_OVERLAP=true
+ENABLE_HIGH_OVERLAP=false
+
+# Benchmark execution controls.
+BENCHMARK_MIN_SAMPLES=2
+BENCHMARK_MAX_SAMPLES=5
+BENCHMARK_TARGET_TOTAL_MS=800
+
+# Select which algorithms are included in the benchmark run.
+ENABLE_BITSET=true
+ENABLE_SIMD_BITSET=false
+ENABLE_STD_HASH=true
+ENABLE_CUSTOM_HASH=true
+ENABLE_SORTED_MERGE=true
+
+# Select which benchmark phases are emitted.
+ENABLE_PREPARE_PHASE=true
+ENABLE_INTERSECTION_PHASE=true
+
+# Select how benchmark output is rendered.
+OUTPUT_FORMAT=markdown
+
+# Select which extra harness steps are counted inside each timed sample.
+TIME_PREPARE_INCLUDE_INPUT_GENERATION=false
+TIME_INTERSECTION_INCLUDE_OUTPUT_CLEAR=false
+TIME_INTERSECTION_INCLUDE_RESULT_COUNT=false