Refactor core package

Author: raharrison

CLAUDE.md

@@ -114,7 +114,7 @@ The project includes runnable GUI applications with `main` methods:
 
 1. **MainFrame** (`uk.co.ryanharrison.mathengine.gui.MainFrame`) - Interactive expression evaluator with graphical interface
 2. **Converter** (`uk.co.ryanharrison.mathengine.gui.Converter`) - Unit conversion tool with GUI
-3. **Grapher** (`uk.co.ryanharrison.mathengine.plotting.Grapher`) - Function plotter with pan/zoom
+3. **Grapher** (`uk.co.ryanharrison.mathengine.gui.Grapher`) - Function plotter with pan/zoom
 
 ## Core Architecture
 
@@ -192,7 +192,8 @@ Central state object holding:
 
 ### Function Class - Single-Variable Equations
 
-The `Function` class (`uk.co.ryanharrison.mathengine.Function`) is the primary interface for packages like differential, integral,
+The `Function` class (`uk.co.ryanharrison.mathengine.core.Function`) is the primary interface for packages like differential,
+integral,
 solvers, and plotting.
 
 **Usage Pattern**: