web: fix schematic port_directions and dark mode visibility

Add missing field(std::string, const char*) overload to JsonBuilder.
Without it, field(getName(), ioTypeToDirection()) resolved to the
bool overload (standard pointer-to-bool conversion beats user-defined
const char*-to-string), writing true instead of "input"/"output"/"inout".

Invert netlistsvg SVG colors in dark mode so strokes and text are
visible against the dark background.

Signed-off-by: Matt Liberty <mliberty@precisioninno.com>

Author: maliberty

src/web/src/json_builder.h

@@ -155,6 +155,10 @@ class JsonBuilder
     buf_ += val ? "true" : "false";
   }
 
+  void field(const std::string& key, const char* val)
+  {
+    field(key.c_str(), val);
+  }
   void field(const std::string& key, int val) { field(key.c_str(), val); }
   void field(const std::string& key, float val) { field(key.c_str(), val); }
   void field(const std::string& key, double val) { field(key.c_str(), val); }

src/web/src/style.css

@@ -1214,3 +1214,10 @@ html, body {
     flex-direction: column;
     gap: 4px;
 }
+
+/* ─── Schematic Widget ────────────────────────────────────────────────────── */
+
+/* netlistsvg renders dark strokes/text on white fills — invert for dark mode */
+html[data-theme="dark"] .schematic-widget svg {
+    filter: invert(1) hue-rotate(180deg);
+}

src/web/test/cpp/TestRequestHandler.cpp

@@ -126,6 +126,24 @@ TEST(JsonEscapeTest, ControlChars)
   EXPECT_EQ(json_escape(input), "\\u0001");
 }
 
+//------------------------------------------------------------------------------
+// JsonBuilder overload tests
+//------------------------------------------------------------------------------
+
+// Verify that field(std::string, const char*) writes a JSON string, not a bool.
+// Without an explicit overload, C++ prefers the standard pointer-to-bool
+// conversion over the user-defined const char*-to-std::string conversion,
+// silently writing "true" instead of the intended string value.
+TEST(JsonBuilderTest, FieldStringKeyCharPtrValueWritesString)
+{
+  JsonBuilder b;
+  b.beginObject();
+  b.field(std::string("dir"), "input");
+  b.endObject();
+  EXPECT_NE(b.str().find("\"input\""), std::string::npos);
+  EXPECT_EQ(b.str().find("true"), std::string::npos);
+}
+
 //------------------------------------------------------------------------------
 // dispatch_request tests (BOUNDS, LAYERS, INFO)
 //------------------------------------------------------------------------------