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/weaseljson_schemagen.py

@@ -690,19 +690,35 @@ namespace {ns} {{"""
         lines.append("  }")
         return "\n".join(lines)
 
-    def _bitmask(self, obj, pred):
-        mask = 0
-        for i, fld in enumerate(obj.fields):
-            if pred(fld):
-                mask |= 1 << i
-        return mask
+    def _fieldcount(self):
+        lines = ["  int fieldCount(Kind k) const {", "    switch (k) {"]
+        for name, obj in self.b.objects.items():
+            lines.append(f"    case Kind::{name}: return {len(obj.fields)};")
+        lines.append("    default: return 0;")
+        lines.append("    }")
+        lines.append("  }")
+        return "\n".join(lines)
 
     def _reqmask(self):
-        lines = ["  uint32_t requiredMask(Kind k) const {", "    switch (k) {"]
+        lines = [
+            "  const std::vector<uint64_t> &requiredMask(Kind k) const {",
+            "    switch (k) {",
+        ]
         for name, obj in self.b.objects.items():
-            m = self._bitmask(obj, lambda f: f.required)
-            lines.append(f"    case Kind::{name}: return {hex(m)}u;")
-        lines.append("    default: return 0u;")
+            words = (len(obj.fields) + 63) // 64
+            req = [0] * words
+            for i, fld in enumerate(obj.fields):
+                if fld.required:
+                    req[i >> 6] |= 1 << (i & 63)
+            init = ", ".join(f"{hex(w)}u" for w in req) if words else ""
+            lines.append(f"    case Kind::{name}: {{")
+            lines.append(f"      static const std::vector<uint64_t> m = {{ {init} }};")
+            lines.append("      return m;")
+            lines.append("    }")
+        lines.append("    default: {")
+        lines.append("      static const std::vector<uint64_t> empty;")
+        lines.append("      return empty;")
+        lines.append("    }")
         lines.append("    }")
         lines.append("  }")
         return "\n".join(lines)
@@ -783,6 +799,11 @@ namespace {ns} {{"""
         if root_kind is not None and root_cat == event_cat:
             lines.append("    if (stack_.empty()) {")
             lines.append(f"      stack_.push_back(Frame{{{root_kind}, &result_}});")
+            if event_cat == "Obj":
+                lines.append("      {")
+                lines.append(f"        int n = fieldCount({root_kind});")
+                lines.append("        stack_.back().seen.assign((n + 63) / 64, 0);")
+                lines.append("      }")
             lines.append("      return;")
             lines.append("    }")
         else:
@@ -798,6 +819,10 @@ namespace {ns} {{"""
         lines.append(f"    if (si.cat != Cat::{event_cat}) {{ reject(); return; }}")
         lines.append("    void *p = engage(f, true);")
         lines.append("    stack_.push_back(Frame{si.child, p});")
+        lines.append("    if (isObjectKind(si.child)) {")
+        lines.append("      int n = fieldCount(si.child);")
+        lines.append("      stack_.back().seen.assign((n + 63) / 64, 0);")
+        lines.append("    }")
         return "\n".join(lines)
 
     def _builder(self, order):
@@ -849,8 +874,8 @@ private:
   struct Frame {{
     Kind kind;
     void *dest;
-    int field = -1;       // object: selected field (-1 want key, -2 skip)
-    uint32_t seen = 0;    // bitmask of populated fields
+    int field = -1;              // object: selected field (-1 want key, -2 skip)
+    std::vector<uint64_t> seen;  // populated field bitset (object frames)
   }};
   static constexpr int kWantKey = -1;
   static constexpr int kSkip = -2;
@@ -885,7 +910,7 @@ private:
     scratch_.clear();
 {("    if (p.kind == Kind::RootScalar) { stack_.pop_back(); done_ = true; return; }" if root_kind is None else "")}
     if (isObjectKind(p.kind)) {{
-      if (p.field >= 0) p.seen |= (1u << p.field);
+      if (p.field >= 0) p.seen[p.field >> 6] |= (1ull << (p.field & 63));
       p.field = kWantKey;
     }}
   }}
@@ -895,16 +920,19 @@ private:
   }}
   void cbEndObject() {{
     if (error_) return;
-    Frame f = stack_.back();
+    Frame &f = stack_.back();
     if (f.kind == Kind::Skip) {{
       stack_.pop_back();
       if (stack_.empty() || stack_.back().kind != Kind::Skip) valueComplete();
       return;
     }}
-    if (isObjectKind(f.kind) &&
-        (f.seen & requiredMask(f.kind)) != requiredMask(f.kind)) {{
-      reject();
-      return;
+    if (isObjectKind(f.kind)) {{
+      const auto &req = requiredMask(f.kind);
+      bool missing = false;
+      for (size_t i = 0; i < req.size(); ++i) {{
+        if ((f.seen[i] & req[i]) != req[i]) {{ missing = true; break; }}
+      }}
+      if (missing) {{ reject(); return; }}
     }}
     stack_.pop_back();
     valueComplete();
@@ -937,7 +965,9 @@ private:
       f.field = kSkip;
       return;
     }}
-    if (f.seen & (1u << idx)) {{ reject(); return; }}  // duplicate key
+    if (f.seen[idx >> 6] & (1ull << (idx & 63))) {{
+      reject(); return;  // duplicate key
+    }}
     f.field = idx;
   }}
 
@@ -1062,6 +1092,8 @@ private:
 
 {self._matchkey()}
 
+{self._fieldcount()}
+
 {self._reqmask()}
 
 {self._is_object_kind()}