feat: Add Vector convenience features - indexing, tuple comparison, floor

Implements issue #109 improvements to mcrfpy.Vector:

- Sequence protocol: v[0], v[1], v[-1], v[-2], len(v), tuple(v), x,y = v
- Tuple comparison: v == (5, 6), v != (1, 2) works bidirectionally
- .floor() method: returns new Vector with floored coordinates
- .int property: returns (int(floor(x)), int(floor(y))) tuple for dict keys

The sequence protocol enables unpacking and iteration, making Vector
interoperable with code expecting tuples. The tuple comparison fixes
compatibility issues where functions returning Vector broke code expecting
tuple comparison (e.g., in Crypt of Sokoban).

Closes #109

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/PyVector.h

@@ -45,15 +45,24 @@ public:
     static PyObject* distance_to(PyVectorObject*, PyObject*);
     static PyObject* angle(PyVectorObject*, PyObject*);
     static PyObject* copy(PyVectorObject*, PyObject*);
+    static PyObject* floor(PyVectorObject*, PyObject*);
+
+    // Sequence protocol
+    static Py_ssize_t sequence_length(PyObject*);
+    static PyObject* sequence_item(PyObject*, Py_ssize_t);
+
+    // Additional properties
+    static PyObject* get_int(PyObject*, void*);
     
     static PyGetSetDef getsetters[];
     static PyMethodDef methods[];
 };
 
 namespace mcrfpydef {
-    // Forward declare the PyNumberMethods structure
+    // Forward declare the PyNumberMethods and PySequenceMethods structures
     extern PyNumberMethods PyVector_as_number;
-    
+    extern PySequenceMethods PyVector_as_sequence;
+
     static PyTypeObject PyVectorType = {
         .ob_base = {.ob_base = {.ob_refcnt = 1, .ob_type = NULL}, .ob_size = 0},
         .tp_name = "mcrfpy.Vector",
@@ -61,6 +70,7 @@ namespace mcrfpydef {
         .tp_itemsize = 0,
         .tp_repr = PyVector::repr,
         .tp_as_number = &PyVector_as_number,
+        .tp_as_sequence = &PyVector_as_sequence,
         .tp_hash = PyVector::hash,
         .tp_flags = Py_TPFLAGS_DEFAULT,
         .tp_doc = PyDoc_STR("SFML Vector Object"),