fix: ensure tests never access ~/.km directory (#1104)

## Summary

- Tests now create isolated temporary directories instead of using
`~/.km`
- Enforces proper test isolation as required by `docs/AGENTS.md`
- Prevents tests from touching user data

## Changes

- **`tests/Main.Tests/Unit/CLI/CliApplicationBuilderTests.cs`**: 
  - Implemented `IDisposable` for proper cleanup
  - Uses temp directory with unique GUID for each test
  - Passes `--config <temp_path>` to avoid `~/.km` access

- **`tests/Main.Tests/Integration/ExamplesCommandOutputTest.cs`**:
  - Creates isolated temp directory for config file
  - Cleans up temp directory in finally block

## Test plan

- [x] All 520 tests pass (306 Core + 214 Main)
- [x] Zero skipped tests
- [x] Code coverage at 83.82% (above 80% threshold)
- [x] `build.sh` passes with 0 warnings
- [x] `format.sh` passes
- [x] `coverage.sh` passes
- [x] Tests no longer access `~/.km` directory

## Compliance

Per `docs/AGENTS.md`:
> "Tests must never read or write files at `~/.km/` - Tests must use
temp dirs"

Author: dluc

tests/Main.Tests/Integration/ExamplesCommandOutputTest.cs

@@ -5,6 +5,7 @@ namespace KernelMemory.Main.Tests.Integration;
 /// <summary>
 /// Test that executes 'km examples' and verifies output contains expected sections.
 /// Uses bash execution to provide proper TTY for Spectre.Console.
+/// This test uses an isolated temp directory to avoid accessing ~/.km.
 /// </summary>
 public sealed class ExamplesCommandOutputTest
 {
@@ -18,15 +19,21 @@ public void KmExamples_ExecutesAndOutputsAllSections()
         var kmDll = Path.Combine(solutionRoot, "src/Main/bin/Debug/net10.0/KernelMemory.Main.dll");
         var outputFile = Path.Combine(Path.GetTempPath(), $"km-examples-test-{Guid.NewGuid():N}.txt");
 
+        // Create isolated temp directory for config to avoid accessing ~/.km
+        var tempDir = Path.Combine(Path.GetTempPath(), $"km-test-{Guid.NewGuid():N}");
+        Directory.CreateDirectory(tempDir);
+        var tempConfigPath = Path.Combine(tempDir, "config.json");
+
         Assert.True(File.Exists(kmDll), $"KernelMemory.Main.dll not found at {kmDll}");
 
         try
         {
-            // Act: Execute km examples via bash and capture output
+            // Act: Execute km examples via bash with isolated config path
+            // Note: --config must come AFTER the command name (Spectre.Console.Cli requirement)
             var process = System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo
             {
                 FileName = "bash",
-                Arguments = $"-c \"dotnet \\\"{kmDll}\\\" examples > \\\"{outputFile}\\\" 2>&1\"",
+                Arguments = $"-c \"dotnet \\\"{kmDll}\\\" examples --config \\\"{tempConfigPath}\\\" > \\\"{outputFile}\\\" 2>&1\"",
                 UseShellExecute = false
             });
 
@@ -79,10 +86,17 @@ public void KmExamples_ExecutesAndOutputsAllSections()
         }
         finally
         {
+            // Clean up output file
             if (File.Exists(outputFile))
             {
                 File.Delete(outputFile);
             }
+
+            // Clean up temp directory
+            if (Directory.Exists(tempDir))
+            {
+                Directory.Delete(tempDir, recursive: true);
+            }
         }
     }
 }

tests/Main.Tests/Unit/CLI/CliApplicationBuilderTests.cs

@@ -4,22 +4,58 @@
 
 namespace KernelMemory.Main.Tests.Unit.CLI;
 
-public sealed class CliApplicationBuilderTests
+/// <summary>
+/// Tests for CliApplicationBuilder.
+/// These tests verify that the CLI application builder correctly creates and configures
+/// command applications. Tests use isolated temp directories to avoid accessing ~/.km.
+/// </summary>
+public sealed class CliApplicationBuilderTests : IDisposable
 {
+    private readonly string _tempDir;
+    private readonly string _tempConfigPath;
+
+    public CliApplicationBuilderTests()
+    {
+        // Create isolated temp directory for each test to avoid ~/.km access
+        this._tempDir = Path.Combine(Path.GetTempPath(), $"km-test-{Guid.NewGuid():N}");
+        Directory.CreateDirectory(this._tempDir);
+        this._tempConfigPath = Path.Combine(this._tempDir, "config.json");
+    }
+
+    public void Dispose()
+    {
+        // Clean up temp directory after test
+        if (Directory.Exists(this._tempDir))
+        {
+            Directory.Delete(this._tempDir, recursive: true);
+        }
+    }
+
     [Fact]
     public void Build_CreatesCommandApp()
     {
+        // Arrange: Use temp config path to avoid accessing ~/.km
         var builder = new CliApplicationBuilder();
-        var app = builder.Build();
+        var args = new[] { "--config", this._tempConfigPath };
+
+        // Act
+        var app = builder.Build(args);
+
+        // Assert
         Assert.NotNull(app);
     }
 
     [Fact]
     public void Configure_SetsApplicationName()
     {
+        // Arrange: Use temp config path to avoid accessing ~/.km
         var builder = new CliApplicationBuilder();
-        var app = builder.Build();
-        // App is configured with name "km"
+        var args = new[] { "--config", this._tempConfigPath };
+
+        // Act
+        var app = builder.Build(args);
+
+        // Assert: App is configured with name "km"
         Assert.NotNull(app);
     }
 }