phase29ad(p0): split pattern6 ok vs contract fixtures

apps/tests/phase29ab_pattern6_matchscan_firstfail_min.hako

@@ -1,5 +1,5 @@
-// Phase 29ac P2: Pattern6 match scan OK minimal
-// Expect: find_missing_step("abc", "b") -> 1
+// Phase 29ad P0: Pattern6 match scan contract violation
+// Expect: JoinIR freeze (step update missing)
 
 static box Main {
     find_missing_step(s, ch) {
@@ -8,7 +8,6 @@ static box Main {
             if s.substring(i, i + 1) == ch {
                 return i
             }
-            i = i + 1
         }
         return -1
     }

apps/tests/phase29ab_pattern6_matchscan_ok_min.hako

@@ -0,0 +1,19 @@
+// Phase 29ac P2: Pattern6 match scan OK minimal
+// Expect: find_ok("abc", "b") -> 1
+
+static box Main {
+    find_ok(s, ch) {
+        local i = 0
+        loop(i < s.length()) {
+            if s.substring(i, i + 1) == ch {
+                return i
+            }
+            i = i + 1
+        }
+        return -1
+    }
+
+    main() {
+        return Main.find_ok("abc", "b")
+    }
+}

apps/tests/phase29ab_pattern6_reverse_firstfail_min.hako

@@ -1,5 +1,5 @@
-// Phase 29ac P1: Pattern6 reverse scan OK minimal
-// Expect: last_index_bad_step("abc", "b") -> 1
+// Phase 29ad P0: Pattern6 reverse scan contract violation
+// Expect: JoinIR freeze (reverse step must be i = i - 1)
 
 static box Main {
     last_index_bad_step(s, ch) {
@@ -8,7 +8,7 @@ static box Main {
             if s.substring(i, i + 1) == ch {
                 return i
             }
-            i = i - 1
+            i = i - 2
         }
         return -1
     }

apps/tests/phase29ab_pattern6_reverse_ok_min.hako

@@ -0,0 +1,19 @@
+// Phase 29ac P1: Pattern6 reverse scan OK minimal
+// Expect: last_index_ok("abc", "b") -> 1
+
+static box Main {
+    last_index_ok(s, ch) {
+        local i = s.length() - 1
+        loop(i >= 0) {
+            if s.substring(i, i + 1) == ch {
+                return i
+            }
+            i = i - 1
+        }
+        return -1
+    }
+
+    main() {
+        return Main.last_index_ok("abc", "b")
+    }
+}