perf: tracking — Aho-Corasick 2x performance gap (coregx/ahocorasick#1)

[kolkov]

Tracking issue for Aho-Corasick performance gap.

coregx/ahocorasick is 2x slower than Rust's aho-corasick crate (38ms vs 18ms on 6MB, 35 patterns). This affects:

• Prefilter for UseDFA with >32 case-fold literals
• UseAhoCorasick strategy (>64 patterns)

Upstream issue: coregx/ahocorasick#1

Impact on coregex

LangArena patterns using AC path:

• bots (?i) — 39 literals, AC prefilter for DFA
• auth_attempts (?i) — 128 → 18 literals (trimmed), now Teddy prefilter
• Any >64 complete literal alternation

Closing the AC gap would improve all AC-dependent patterns by ~2x.