Read transition arrays directly on the match path, bypassing SafeInde…

[MariusVolkhart]

…xable dispatch

The per-character match loop reached every transition, value, and prefix through AhoCorasickStore -> a SafeIndexable field. SafeIndexable is abstract with two implementations (DoubleArrayIntList during build, UnboxedIntList after), so each access was a bimorphic virtual call plus a backing-array field load plus a bounds check. That indirection sat in the hottest loop in the library.

After build() the store is always backed by UnboxedIntList, so the match path can read the raw int[] directly: monomorphic, and the JIT can hoist the array reference and eliminate per-access bounds checks. The build-time and keyValue paths still go through the SafeIndexable accessors, so pre-build mutation (add/replace, which run before buildRuntimeStructures) is unchanged.

Mechanical changes:

• Expose UnboxedIntList.backingArray.
• AhoCorasickStore.buildRuntimeStructures captures the five backing arrays (runtimeBaseOffsets/Parents/Values/FailureIndices/PrefixIndices) once the lists have been converted to UnboxedIntList.
• calculateNextState reads baseOffsets/parents/failureIndices directly; the parentCount bounds check reproduces safeGetParent (out-of-range child has no parent, and RESERVED_VALUE can never equal a non-negative node index).
• AhoCorasickSpliterator captures the value/prefix arrays once and indexes them per result.

Behavior unchanged (full library test suite green). Allocation per op unchanged, as expected — this removes dispatch, not allocation.

ParseBenchmark, 100k dictionary, JDK 25, f2/wi5/i10 (ops/s, higher is better):

config before after delta
ASCII SPARSE 38.5±0.7 43.8±0.8 +13.6%
ASCII DENSE 12.0±0.2 13.7±0.4 +14.6%
UNICODE SPARSE 71.4±1.7 81.2±1.5 +13.8%
UNICODE DENSE 12.0±0.1 13.2±0.2 +9.6%

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