phase: 20.49 COMPLETE; 20.50 Flow+String minimal reps; 20.51 selfhost v0/v1 minimal (Option A/B); hv1-inline binop/unop/copy; docs + run_all + CURRENT_TASK -> 21.0

apps/std/string2.hako

@@ -0,0 +1,18 @@
+// std.string (Ny) - Phase15 MVP
+// Usage:
+//   include "apps/std/string.hako"
+//   StdStringNy.string_length("abc"), StdStringNy.string_concat("a","b"),
+//   StdStringNy.string_slice("hello",1,4), StdStringNy.string_index_of("banana","na"), StdStringNy.string_equals("x","y")
+// Notes:
+//   - ASCII only; slice clamps [start,end)
+//   - index_of returns -1 when not found
+//   - Pure functions; no side effects
+
+static box StdStringNy {
+  string_length(s) {
+    if s == null { return 0 }
+    return s.length()
+  }
+
+  // Keep only length for now to diagnose include hang
+}