Move py_to_notebook.py to bin/ directory for better organization

- Moved tools/py_to_notebook.py to bin/py_to_notebook.py
- Updated tito.py to reference the new location
- Made py_to_notebook.py executable for direct invocation
- Removed empty tools/ directory
- Updated documentation to reflect new location
- All tools now consolidated in bin/ directory for consistency

Benefits:
- Conventional organization (bin/ for executables)
- Can invoke tools directly: ./bin/py_to_notebook.py
- Cleaner project structure
- Consistent with other tools (tito.py, generate_student_notebooks.py)

bin/py_to_notebook.py

@@ -3,8 +3,8 @@
 Convert Python files with cell markers to Jupyter notebooks.
 
 Usage:
-    python3 tools/py_to_notebook.py modules/tensor/tensor_dev.py
-    python3 tools/py_to_notebook.py modules/tensor/tensor_dev.py --output custom_name.ipynb
+    python3 bin/py_to_notebook.py modules/tensor/tensor_dev.py
+    python3 bin/py_to_notebook.py modules/tensor/tensor_dev.py --output custom_name.ipynb
 """
 
 import argparse

bin/tito.py

@@ -824,7 +824,7 @@ def cmd_notebooks(args):
         try:
             # Use the separate py_to_notebook.py tool
             result = subprocess.run([
-                sys.executable, "tools/py_to_notebook.py", str(dev_file)
+                sys.executable, "bin/py_to_notebook.py", str(dev_file)
             ], capture_output=True, text=True)
             
             module_name = dev_file.parent.name

docs/development/module-development-guide.md

@@ -208,7 +208,7 @@ python bin/tito.py notebooks --module {module}
 
 ### Generate Student Version
 ```bash
-python3 bin/generate_student_notebooks.py --module {module}
+python bin/generate_student_notebooks.py --module {module}
 ```
 
 ### Test Complete Workflow

docs/development/quick-module-reference.md

@@ -106,7 +106,7 @@ cp modules/example/example_dev.py modules/{module}/{module}_dev.py
 
 # Full workflow
 python bin/tito.py notebooks --module {module}
-python3 bin/generate_student_notebooks.py --module {module}
+python bin/generate_student_notebooks.py --module {module}
 
 # Test everything
 python bin/tito.py test --module {module}