schemagen: support objects with more than 32 properties

Replace the 32-bit `uint32_t seen` bitmask with a `std::vector<uint64_t>`
bitset sized to the actual field count.  `requiredMask` is now a vector of
the same word count, and required-field checks use per-word masking so that
optional fields do not cause false rejections.

Adds big.schema.json + test_big.cpp regression tests covering the issue
reproducer (40 required properties, missing/duplicate at index 32), plus
run_tests.sh to exercise both test_gen.cpp and test_big.cpp.

Fixes #3

contrib/schemagen/test_big.cpp

@@ -0,0 +1,140 @@
+// Regression test for issue #3: objects with more than 32 properties.
+#include <cassert>
+#include <cstdio>
+#include <string>
+
+#include "big.h"
+
+using namespace big_schema;
+
+static WeaselJsonStatus parseStrided(RootBuilder &b, std::string in) {
+  for (size_t i = 0; i < in.size(); ++i) {
+    char c = in[i];
+    WeaselJsonStatus s = b.feed(&c, 1);
+    if (s != WeaselJson_AGAIN)
+      return s;
+  }
+  return b.finish();
+}
+
+static int failures = 0;
+#define CHECK(cond)                                                            \
+  do {                                                                         \
+    if (!(cond)) {                                                             \
+      printf("FAIL %s:%d: %s\n", __FILE__, __LINE__, #cond);                   \
+      ++failures;                                                              \
+    }                                                                          \
+  } while (0)
+
+static void expectReject(const std::string &json, const char *what) {
+  RootBuilder b;
+  WeaselJsonStatus s = parseStrided(b, json);
+  if (s == WeaselJson_REJECT) {
+    printf("ok   reject: %s\n", what);
+  } else {
+    printf("FAIL expected reject (%s) got status %d for: %s\n", what, s,
+           json.c_str());
+    ++failures;
+  }
+}
+
+static std::string all40() {
+  std::string json = "{";
+  for (int i = 0; i < 40; ++i) {
+    if (i)
+      json += ",";
+    json += "\"p" + std::to_string(i) + "\":\"v" + std::to_string(i) + "\"";
+  }
+  json += "}";
+  return json;
+}
+
+int main() {
+  // All 40 required fields present -> accepted, values land in right slots.
+  {
+    RootBuilder b;
+    std::string json = all40();
+    WeaselJsonStatus s = parseStrided(b, json);
+    CHECK(s == WeaselJson_OK);
+    if (s == WeaselJson_OK) {
+      Root r = b.take();
+      CHECK(r.p0 == "v0");
+      CHECK(r.p31 == "v31");
+      CHECK(r.p32 == "v32");
+      CHECK(r.p39 == "v39");
+      printf("ok   all 40 required fields accepted\n");
+    }
+  }
+
+  // Missing field p32 (index 32) must be detected, not aliased to bit 0.
+  {
+    std::string json = all40();
+    // Remove the p32 entry: find its substring and erase it.
+    std::string entry = "\"p32\":\"v32\"";
+    size_t pos = json.find(entry);
+    assert(pos != std::string::npos);
+    // Remove the trailing comma before it if present, or the leading comma
+    // after it.
+    if (pos > 0 && json[pos - 1] == ',') {
+      json.erase(pos - 1, entry.size() + 1);
+    } else if (pos + entry.size() < json.size() &&
+               json[pos + entry.size()] == ',') {
+      json.erase(pos, entry.size() + 1);
+    } else {
+      json.erase(pos, entry.size());
+    }
+    expectReject(json, "missing required field p32 (index 32)");
+  }
+
+  // Missing p0 still rejected.
+  {
+    std::string json = all40();
+    std::string entry = "\"p0\":\"v0\"";
+    size_t pos = json.find(entry);
+    assert(pos != std::string::npos);
+    if (json[pos + entry.size()] == ',') {
+      json.erase(pos, entry.size() + 1);
+    } else {
+      json.erase(pos, entry.size());
+    }
+    expectReject(json, "missing required field p0");
+  }
+
+  // Duplicate keys p0 and p32 must both be detected.
+  {
+    std::string json = all40();
+    // Insert p32 again right after the existing p32 entry.
+    std::string entry = "\"p32\":\"v32\"";
+    size_t pos = json.find(entry);
+    assert(pos != std::string::npos);
+    json.insert(pos + entry.size(), ",\"p32\":\"dup\"");
+    expectReject(json, "duplicate key p32 (index 32)");
+  }
+
+  // Duplicate keys p0 and p31 cover boundary bits.
+  {
+    std::string json = all40();
+    std::string entry = "\"p0\":\"v0\"";
+    size_t pos = json.find(entry);
+    assert(pos != std::string::npos);
+    json.insert(pos + entry.size(), ",\"p0\":\"dup\"");
+    expectReject(json, "duplicate key p0");
+  }
+
+  // Duplicate p31/p32 around the 32-bit boundary.
+  {
+    std::string json = all40();
+    std::string entry = "\"p31\":\"v31\"";
+    size_t pos = json.find(entry);
+    assert(pos != std::string::npos);
+    json.insert(pos + entry.size(), ",\"p31\":\"dup\"");
+    expectReject(json, "duplicate key p31");
+  }
+
+  if (failures == 0) {
+    printf("\nALL TESTS PASSED\n");
+    return 0;
+  }
+  printf("\n%d FAILURE(S)\n", failures);
+  return 1;
+}