Organize test suite: add README, move loose tests to proper directories

- Add tests/README.md documenting test structure and usage
- Move issue_*_test.py files to tests/regression/ (9 files)
- Move loose test_*.py files to tests/unit/ (18 files)
- tests/ root now contains only pytest infrastructure

Addresses #166

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/unit/test_frame_bounds.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+"""Test Frame bounds"""
+import sys
+import mcrfpy
+
+print("Testing Frame bounds...")
+frame = mcrfpy.Frame(pos=(50, 100), size=(200, 150))
+
+print(f"Frame created: {frame}")
+
+# Test bounds returns tuple of Vectors
+bounds = frame.bounds
+print(f"bounds type: {type(bounds)}")
+print(f"bounds value: {bounds}")
+
+if not isinstance(bounds, tuple):
+    print(f"FAIL: bounds should be tuple, got {type(bounds)}")
+    sys.exit(1)
+
+if len(bounds) != 2:
+    print(f"FAIL: bounds should have 2 elements, got {len(bounds)}")
+    sys.exit(1)
+
+pos, size = bounds
+print(f"pos type: {type(pos)}, value: {pos}")
+print(f"size type: {type(size)}, value: {size}")
+
+if not hasattr(pos, 'x'):
+    print(f"FAIL: pos should be Vector (has no .x), got {type(pos)}")
+    sys.exit(1)
+
+print(f"pos.x={pos.x}, pos.y={pos.y}")
+print(f"size.x={size.x}, size.y={size.y}")
+
+# Test get_bounds() method is removed (#185)
+if hasattr(frame, 'get_bounds'):
+    print("FAIL: get_bounds() method should be removed")
+    sys.exit(1)
+else:
+    print("PASS: get_bounds() method is removed")
+
+print("PASS: Frame bounds test passed!")
+sys.exit(0)