feat: Add geometry module demo system for orbital mechanics

Creates comprehensive visual demonstrations of the geometry module:

Static demos:
- Bresenham algorithms: circle/line rasterization on grid cells
- Angle calculations: line elements showing angles between points,
  waypoint viability with angle thresholds, orbit exit headings
- Pathfinding: planets with surfaces and orbit rings, optimal
  path using orbital slingshots vs direct path comparison

Animated demos:
- Solar system: planets orbiting star with discrete time steps,
  nested moon orbit, position updates every second
- Pathfinding through moving system: ship navigates to target
  using orbital intercepts, anticipating planetary motion

Includes 5 screenshot outputs demonstrating each feature.

Run: ./mcrogueface --headless --exec tests/geometry_demo/geometry_main.py
Interactive: ./mcrogueface tests/geometry_demo/geometry_main.py

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

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

tests/geometry_demo/screens/base.py

@@ -0,0 +1,84 @@
+"""Base class for geometry demo screens."""
+import mcrfpy
+import sys
+import os
+
+# Add scripts path for geometry module
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..', '..', 'src', 'scripts'))
+from geometry import *
+
+
+class GeometryDemoScreen:
+    """Base class for geometry demo screens."""
+
+    name = "Base Screen"
+    description = "Override this description"
+
+    def __init__(self, scene_name):
+        self.scene_name = scene_name
+        mcrfpy.createScene(scene_name)
+        self.ui = mcrfpy.sceneUI(scene_name)
+        self.timers = []  # Track timer names for cleanup
+
+    def setup(self):
+        """Override to set up the screen content."""
+        pass
+
+    def cleanup(self):
+        """Clean up timers when leaving screen."""
+        for timer_name in self.timers:
+            try:
+                mcrfpy.delTimer(timer_name)
+            except:
+                pass
+
+    def get_screenshot_name(self):
+        """Return the screenshot filename for this screen."""
+        return f"{self.scene_name}.png"
+
+    def add_title(self, text, y=10):
+        """Add a title caption."""
+        title = mcrfpy.Caption(text=text, pos=(400, y))
+        title.fill_color = mcrfpy.Color(255, 255, 255)
+        title.outline = 2
+        title.outline_color = mcrfpy.Color(0, 0, 0)
+        self.ui.append(title)
+        return title
+
+    def add_description(self, text, y=50):
+        """Add a description caption."""
+        desc = mcrfpy.Caption(text=text, pos=(50, y))
+        desc.fill_color = mcrfpy.Color(200, 200, 200)
+        self.ui.append(desc)
+        return desc
+
+    def add_label(self, text, x, y, color=(200, 200, 200)):
+        """Add a label caption."""
+        label = mcrfpy.Caption(text=text, pos=(x, y))
+        label.fill_color = mcrfpy.Color(*color)
+        self.ui.append(label)
+        return label
+
+    def create_grid(self, grid_size, pos, size, cell_size=16):
+        """Create a grid for visualization."""
+        grid = mcrfpy.Grid(
+            grid_size=grid_size,
+            pos=pos,
+            size=size
+        )
+        grid.fill_color = mcrfpy.Color(20, 20, 30)
+        self.ui.append(grid)
+        return grid
+
+    def color_grid_cell(self, grid, x, y, color):
+        """Color a specific grid cell."""
+        try:
+            point = grid.at(x, y)
+            point.color = mcrfpy.Color(*color) if isinstance(color, tuple) else color
+        except:
+            pass  # Out of bounds
+
+    def add_timer(self, name, callback, interval):
+        """Add a timer and track it for cleanup."""
+        mcrfpy.setTimer(name, callback, interval)
+        self.timers.append(name)