- TestFatTeddyAVX2_SingleLaneBuckets: verifies GET/POST/PUT found
  with patterns distributed across specific lanes
- TestFatTeddyCaseFoldRegression: validates match count vs stdlib
  for (?i)get|post|put via meta-engine (750/750 on 1000 log lines)

FatTeddy AVX2 is now correct (ORL fix). Remove:
- buildACPrefilter: replaced ALL FatTeddy with AC (workaround)
- ac_prefilter.go: AC wrapper type (unused)
- fatTeddyFallback path in findIndicesTeddyAt (FatTeddy handles all sizes)

LangArena methods (?i)get|post|put: AC 41ms → FatTeddy 11ms

isMatchDFA now loops through prefilter candidates and verifies each with
anchored DFA instead of single unanchored PikeVM scan from first candidate.

Issue #137 match case: 176us → 27us (6.5x faster, 3.7x faster than stdlib)

…states)

For patterns with >100 NFA states (e.g., (?i) case-fold), bidirectional DFA
cache-thrashes. Prefilter candidate loop with anchored DFA verification
avoids building full DFA state table.

Guard: nfaStateCount > 100 — small NFAs (34-57 states) use bidirectional
DFA directly (no cache thrashing, lower overhead than candidate loop).

Also adds nfaStateCount field to Engine for the guard check.

When >64 literals extracted, try cascading trim: keep 4 bytes → dedup,
if still >64 → keep 3 bytes → dedup, if still >64 → keep 2 bytes → dedup.
Falls back to original if trimming can't reduce below 64.

Matches Rust's optimize_for_prefix_by_preference ATTEMPTS table.
auth_attempts (?i)/login|/signin: 128 literals → 18 four-byte → Teddy.
34ms → 10ms.

Batch ASM: fatTeddyAVX2_2_batch scans entire haystack in one call,
writes all (pos, bucketMask) candidates to pre-allocated buffer.
Eliminates Go→ASM round trip overhead (11.6 GB/s SIMD vs 283 MB/s with round trips).

FindAllPositions: batch-based FindAll using single ASM call.
Find: uses original per-candidate path (batch too slow for first-match).

Flat DFA with premultiplied state IDs, match flag in high bit,
SIMD skip-ahead prefilter via bytes.IndexByte.

Throughput: Find 3.4 GB/s, IsMatch 5.9-7.0 GB/s (was 260-545 MB/s).