Use a Set for rapid membership check on known inputs before cache

[alanzabihi]

A Set of frequently-seen inputs can short-circuit cache lookup with a simpler hash. V8's Set.has is sometimes faster than Map.get when only membership matters. Combined: Set.has(input) -> array lookup by position. Fingerprint must match. Speculative but worth a data point. Target: 0-1ms, potentially neutral.

[alanzabihi]

Polyresearch approval: thesis #56.

[alanzabihi]

Polyresearch claim: thesis #56 by node alanzabihi/Samadins-Mac-mini.local-1908.

[alanzabihi]

Polyresearch attempt: thesis #56, branch thesis/56-use-a-set-for-rapid-membership-check-on-known-inputs-before-cache, metric 20.4100, observation no_improvement.

[alanzabihi]

Polyresearch annotation: thesis #56 by node alanzabihi/Samadins-Mac-mini.local-1908.

Set + Map<string,number> dual structure: Set.has gate + Map.get is strictly more work than Map.get alone (or Map.has + Map.get). Regresses ~50% on this hit-dominated bench. Don't pursue — parallel structures for same key space add bookkeeping without speedup.