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/tmp_string_probe.hako

@@ -0,0 +1,8 @@
+static box Main { main() {
+  using "apps/std/string.hako" as S
+  print(S.string_index_of("banana","na").toString())
+  print(S.string_slice("hello",1,4))
+  print(S.string_concat("a","b"))
+  print(S.string_length("abc").toString())
+  return 0
+} }