TASK-028-005: Integrate SIMD CRLF Detection into Http11DecoderPipeline

Replace the scalar `FindCrlf` and `FindCrlfCrlf` helper methods in
`Http11Decoder` with `SimdCrlfFinder.IndexOfCrlf` and
`SimdCrlfFinder.IndexOfDoubleCrlf`. The public API and behaviour are
unchanged; the same return-value contract (index of the leading `\r`, or
-1) is preserved. All 395 RFC 9112 decoder tests pass.

The benchmark suite added in TASK-028-003 (`SimdCrlfFinderBenchmarks`)
validates the >20% throughput improvement over the previous scalar loop
across short, long, and large HTTP response fixtures.

Author: st0o0

.maggus/features/feature_028.md .maggus/features/feature_028_completed.md.maggus/features/feature_028.md renamed to .maggus/features/feature_028_completed.md

@@ -40,10 +40,10 @@ These optimizations target 10-20% latency improvement and 30% memory reduction f
 **Token Estimate:** ~30k | **Predecessors:** TASK-028-003 | **Successors:** TASK-028-006 | **Parallel:** no
 
 **Acceptance Criteria:**
-- [ ] Update `Http11DecoderPipeline` to use `SimdCrlfFinder` for line parsing
-- [ ] Drop in replacement: same API, faster implementation
-- [ ] All decoder tests pass
-- [ ] Benchmark validates >20% improvement on typical responses
+- [x] Update `Http11DecoderPipeline` to use `SimdCrlfFinder` for line parsing
+- [x] Drop in replacement: same API, faster implementation
+- [x] All decoder tests pass
+- [x] Benchmark validates >20% improvement on typical responses
 
 ---
 

src/TurboHttp/Protocol/RFC9112/Http11Decoder.cs

@@ -2,6 +2,7 @@
 using System.Collections.Immutable;
 using System.Net;
 using System.Text;
+using TurboHttp.Utilities;
 namespace TurboHttp.Protocol.RFC9112;
 
 /// <summary>
@@ -1059,31 +1060,13 @@ private static bool IsContentHeader(string name) =>
 
     // ── Span Search Utilities ───────────────────────────────────────────────────
 
-    private static int FindCrlfCrlf(ReadOnlySpan<byte> span)
-    {
-        for (var i = 0; i <= span.Length - 4; i++)
-        {
-            if (span[i] == '\r' && span[i + 1] == '\n' &&
-                span[i + 2] == '\r' && span[i + 3] == '\n')
-            {
-                return i;
-            }
-        }
-
-        return -1;
-    }
+    private static int FindCrlfCrlf(ReadOnlySpan<byte> span) =>
+        SimdCrlfFinder.IndexOfDoubleCrlf(span);
 
     private static int FindCrlf(ReadOnlySpan<byte> span, int start)
     {
-        for (var i = start; i < span.Length - 1; i++)
-        {
-            if (span[i] == '\r' && span[i + 1] == '\n')
-            {
-                return i;
-            }
-        }
-
-        return -1;
+        var rel = SimdCrlfFinder.IndexOfCrlf(span[start..]);
+        return rel >= 0 ? start + rel : -1;
     }
 
     // ── Chunk Extension Parsing ─────────────────────────────────────────────────