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/libs/json_cur.hako

@@ -0,0 +1,67 @@
+// JsonCursorBox: minimal JSON scanning helpers (Nyash)
+// Note: naive and partial; sufficient for MVP patterns (string/int + bracket depth)
+static box JsonCursorBox {
+  next_non_ws(s, pos) {
+    local i = pos
+    local n = s.length()
+    loop (i < n) {
+      local ch = s.substring(i, i+1)
+      if ch != " " && ch != "\n" && ch != "\r" && ch != "\t" { return i }
+      i = i + 1
+    }
+    return -1
+  }
+  read_quoted_from(s, pos) {
+    local i = pos
+    if s.substring(i, i+1) != "\"" { return "" }
+    i = i + 1
+    local out = ""
+    local n = s.length()
+    loop (i < n) {
+      local ch = s.substring(i, i+1)
+      if ch == "\"" { break }
+      if ch == "\\" { i = i + 1  ch = s.substring(i, i+1) }
+      out = out + ch
+      i = i + 1
+    }
+    return out
+  }
+  read_digits_from(s, pos) {
+    local out = ""
+    local i = pos
+    if i == null { return out }
+    if i < 0 { return out }
+    loop (true) {
+      local ch = s.substring(i, i+1)
+      if ch == "" { break }
+      if ch == "0" || ch == "1" || ch == "2" || ch == "3" || ch == "4" || ch == "5" || ch == "6" || ch == "7" || ch == "8" || ch == "9" { out = out + ch  i = i + 1 } else { break }
+    }
+    return out
+  }
+  find_balanced_array_end(s, idx) {
+    local n = s.length()
+    if s.substring(idx, idx+1) != "[" { return -1 }
+    local depth = 0
+    local i = idx
+    loop (i < n) {
+      local ch = s.substring(i, i+1)
+      if ch == "[" { depth = depth + 1 }
+      if ch == "]" { depth = depth - 1  if depth == 0 { return i } }
+      i = i + 1
+    }
+    return -1
+  }
+  find_balanced_object_end(s, idx) {
+    local n = s.length()
+    if s.substring(idx, idx+1) != "{" { return -1 }
+    local depth = 0
+    local i = idx
+    loop (i < n) {
+      local ch = s.substring(i, i+1)
+      if ch == "{" { depth = depth + 1 }
+      if ch == "}" { depth = depth - 1  if depth == 0 { return i } }
+      i = i + 1
+    }
+    return -1
+  }
+}