source gen and ir gen now use the same seq generator

StgSharp.RegularAnalysis/Text/RegexAnalyzer.PrefixEmit.cs

@@ -18,7 +18,8 @@ namespace StgSharp.RegularAnalysis.Text
     {
 
         internal static List<RegexIR> EmitPrefix(
-                                      List<RegexIR> irList
+                                      List<RegexIR> irList,
+                                      ref RegexInfo info
         )
         {
             List<RegexIR> origin = irList;
@@ -27,8 +28,9 @@ namespace StgSharp.RegularAnalysis.Text
 
             int region_name = 1;
             EmitPrefix(origin_span, result, 0, 0);
-            FixLineObservation(result);
-
+            int single_line_count = FixLineObservation(result);
+            info.RegionCount = region_name - 1;
+            info.SingleLineResultCount = single_line_count;
             return result;
 
             void EmitPrefix(
@@ -408,10 +410,14 @@ namespace StgSharp.RegularAnalysis.Text
                 }
             }
 
-            static void FixLineObservation(
-                        List<RegexIR> result
+            static int FixLineObservation(
+                       List<RegexIR> result
             )
             {
+                // Observe_Line uses relative offsets while nested regions are emitted.
+                // Positive offsets point to larger line numbers; this pass resolves them
+                // into absolute IR line indexes after the final instruction order is known.
+                HashSet<int> single_required = [];
                 for (int i = 0; i < result.Count; i++)
                 {
                     RegexIRPrefix prefix = result[i].Prefix;
@@ -420,11 +426,15 @@ namespace StgSharp.RegularAnalysis.Text
                         continue;
                     }
 
-                    result[i].Prefix = new RegexIRPrefix(
+                    int observeSource = i + prefix.ObserveSource;
+                    RegexIRPrefix prefix_new = new RegexIRPrefix(
                         prefix.WorkingRegion,
                         prefix.Mask,
-                        i - 1);
+                        observeSource);
+                    result[i].Prefix = prefix_new;
+                    _ = single_required.Add(prefix_new.ObserveSource);
                 }
+                return single_required.Count;
             }
 
             static bool IsFoldableSingleTryInstruction(