feat: add sample project and point demo workflow at it

Adds samples/SampleProject/ with a small class hierarchy (interfaces,
service, calculator) that produces a meaningful graph for the live demo.

The code-graph workflow now analyzes ./samples instead of the entire
repo, making the GitHub Pages visualization a proper showcase rather
than a confusing self-graph of the analyzer's own internals.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: TheSmallPixel

.github/workflows/code-graph.yml

@@ -2,18 +2,19 @@ name: "Generate Code Graph"
 
 on:
   push:
-    branches: [ "main" ]
+    branches: [main]
 
 permissions:
-  contents: write 
+  contents: write
+
 jobs:
   generate-graph:
     runs-on: ubuntu-latest
     steps:
       - name: Code Graph
         uses: TheSmallPixel/GraphCSharp@main
         with:
-          source-path: "./"
+          source-path: "./samples"
           docs-dir: "docs"
           index-file: "index.html"
           commit-changes: "true"

samples/SampleProject/Calculator.cs

@@ -0,0 +1,14 @@
+namespace SampleProject;
+
+public class Calculator
+{
+    public int Add(int a, int b) => a + b;
+    public int Subtract(int a, int b) => a - b;
+    public int Multiply(int a, int b) => a * b;
+
+    public double Divide(int a, int b)
+    {
+        if (b == 0) throw new DivideByZeroException();
+        return (double)a / b;
+    }
+}

samples/SampleProject/Formatter.cs

@@ -0,0 +1,16 @@
+namespace SampleProject;
+
+public interface IFormatter
+{
+    string Format(string input);
+}
+
+public class UpperCaseFormatter : IFormatter
+{
+    public string Format(string input) => input.ToUpperInvariant();
+}
+
+public class LowerCaseFormatter : IFormatter
+{
+    public string Format(string input) => input.ToLowerInvariant();
+}

samples/SampleProject/GreetingService.cs

@@ -0,0 +1,22 @@
+namespace SampleProject;
+
+public interface IGreetingService
+{
+    string Greet(string name);
+}
+
+public class GreetingService : IGreetingService
+{
+    private readonly IFormatter _formatter;
+
+    public GreetingService()
+    {
+        _formatter = new UpperCaseFormatter();
+    }
+
+    public string Greet(string name)
+    {
+        var raw = $"Hello, {name}!";
+        return _formatter.Format(raw);
+    }
+}

samples/SampleProject/Program.cs

@@ -0,0 +1,14 @@
+namespace SampleProject;
+
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        var service = new GreetingService();
+        var message = service.Greet("World");
+        Console.WriteLine(message);
+
+        var calculator = new Calculator();
+        Console.WriteLine($"2 + 3 = {calculator.Add(2, 3)}");
+    }
+}