Improve terse docstrings on Vector, Font, Texture, GridPoint, GridPointState

Replace placeholder docstrings ("SFML Vector Object", "SFML Font Object",
etc.) with comprehensive constructor signatures, argument descriptions,
and property listings matching the documentation standard used by other
types like Color and Frame.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/PyFont.h

@@ -38,7 +38,15 @@ namespace mcrfpydef {
         .tp_repr = PyFont::repr,
         //.tp_hash = PyFont::hash,
         .tp_flags = Py_TPFLAGS_DEFAULT,
-        .tp_doc = PyDoc_STR("SFML Font Object"),
+        .tp_doc = PyDoc_STR(
+            "Font(filename: str)\n\n"
+            "A font resource for rendering text in Caption elements.\n\n"
+            "Args:\n"
+            "    filename: Path to a TrueType (.ttf) or OpenType (.otf) font file.\n\n"
+            "Properties:\n"
+            "    family (str, read-only): Font family name from metadata.\n"
+            "    source (str, read-only): File path used to load this font.\n"
+        ),
         .tp_getset = PyFont::getsetters,
         //.tp_base = &PyBaseObject_Type,
         .tp_init = (initproc)PyFont::init,