feat: add .NET host process integration

Implements native host process support with .NET backend:
- Add .NET host project with HTTP endpoints (health check, hello world)
- Configure multi-platform host executables in addon.json
- Add host communication methods in main process
- Create host demo tab in UI
- Add .gitignore for .NET build artifacts

The host process runs on a dynamic port and communicates via HTTP with the main addon process.

.gitignore

@@ -0,0 +1,17 @@
+# .NET build outputs
+host/bin/
+host/obj/
+host/win-x64/
+host/linux-x64/
+host/osx-x64/
+host/osx-arm64/
+
+# IDE
+.vs/
+.vscode/
+*.user
+*.suo
+
+# OS
+.DS_Store
+Thumbs.db

addon.json

@@ -29,8 +29,19 @@
   "_comment_renderer": "Optional: Path to renderer process module for UI components",
   "renderer": "renderer/index.js",
 
-  "_comment_host": "Optional: Native host process configuration (for .NET, Go, Rust, etc.)",
+  "_comment_host": "Native host process configuration (.NET backend)",
-  "_comment_host_note": "Remove this section if your addon is pure JavaScript",
+  "host": {
+    "directory": "host",
+    "executable": "MyFirstAddon.Host",
+    "platforms": {
+      "win-x64": "host/win-x64/MyFirstAddon.Host.exe",
+      "linux-x64": "host/linux-x64/MyFirstAddon.Host",
+      "osx-x64": "host/osx-x64/MyFirstAddon.Host",
+      "osx-arm64": "host/osx-arm64/MyFirstAddon.Host"
+    },
+    "healthCheck": "/health",
+    "startupTimeout": 10000
+  },
 
   "_comment_permissions": "Required permissions - user sees these before installing",
   "permissions": [

host/MyFirstAddon.Host.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <AssemblyName>MyFirstAddon.Host</AssemblyName>
+    <RootNamespace>MyFirstAddon.Host</RootNamespace>
+  </PropertyGroup>
+
+</Project>

host/Program.cs

@@ -0,0 +1,35 @@
+var builder = WebApplication.CreateBuilder(args);
+
+// Configure port from environment variable (set by GitCaddy AddonManager)
+var port = Environment.GetEnvironmentVariable("ADDON_HOST_PORT") ?? "47933";
+builder.WebHost.UseUrls($"http://127.0.0.1:{port}");
+
+var app = builder.Build();
+
+// Root endpoint
+app.MapGet("/", () => new {
+    status = "ok",
+    service = "MyFirstAddon.Host",
+    version = "1.0.0"
+});
+
+// Health check endpoint (required by GitCaddy)
+app.MapGet("/health", () => new {
+    status = "healthy",
+    timestamp = DateTime.UtcNow
+});
+
+// Hello World endpoint - demonstrates a simple addon host function
+app.MapGet("/hello", () => new {
+    message = "Hello World from MyFirstAddon.Host!",
+    timestamp = DateTime.UtcNow
+});
+
+// Hello endpoint with name parameter
+app.MapGet("/hello/{name}", (string name) => new {
+    message = $"Hello, {name}!",
+    timestamp = DateTime.UtcNow
+});
+
+Console.WriteLine($"MyFirstAddon.Host starting on http://127.0.0.1:{port}");
+app.Run();

main/index.js

@@ -201,6 +201,11 @@ class MyFirstAddon {
       case 'performAction':
         return this.performAction(args[0]);
 
+      // ---- Host Methods ----
+      // These call the .NET host process
+      case 'callHelloWorld':
+        return this.callHelloWorld(args[0]);
+
       // ---- Capability Methods ----
       // These are called by GitCaddy for registered capabilities
       case 'generateCommitMessage':
@@ -460,6 +465,46 @@ class MyFirstAddon {
     };
   }
 
+  // ============================================================
+  // HOST METHODS
+  // These methods communicate with the .NET host process
+  // ============================================================
+
+  /**
+   * Call the Hello World endpoint on the .NET host.
+   *
+   * Demonstrates how to communicate with a native host process.
+   *
+   * @param {string} [name] - Optional name to greet
+   * @returns {Promise<{message: string, timestamp: string}>}
+   */
+  async callHelloWorld(name) {
+    if (!this.context?.hostPort) {
+      this.context?.log.warn('Host port not available - host may not be running');
+      return { error: 'Host not available', message: null };
+    }
+
+    try {
+      const endpoint = name
+        ? `http://127.0.0.1:${this.context.hostPort}/hello/${encodeURIComponent(name)}`
+        : `http://127.0.0.1:${this.context.hostPort}/hello`;
+
+      this.context?.log.info(`Calling host endpoint: ${endpoint}`);
+
+      const response = await fetch(endpoint);
+      if (!response.ok) {
+        throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+      }
+
+      const result = await response.json();
+      this.context?.log.info('Host response:', result);
+      return result;
+    } catch (error) {
+      this.context?.log.error('Failed to call host:', error);
+      return { error: error.message, message: null };
+    }
+  }
+
   // ============================================================
   // EVENT HANDLERS
   // ============================================================

views/demo.html

@@ -310,6 +310,7 @@
     <button class="tab active" data-tab="overview">Overview</button>
     <button class="tab" data-tab="actions">Actions</button>
     <button class="tab" data-tab="ipc">IPC Demo</button>
+    <button class="tab" data-tab="host">Host Demo</button>
     <button class="tab" data-tab="logs">Logs</button>
   </div>
 
@@ -420,6 +421,46 @@
     </div>
   </div>
 
+  <!-- Host Demo Tab -->
+  <div id="host" class="tab-content">
+    <div class="section">
+      <h2>.NET Host Communication</h2>
+      <p>
+        This addon includes a .NET native host process that provides HTTP endpoints.
+        GitCaddy automatically starts the host when the addon is activated and
+        provides the port number via <code>context.hostPort</code>.
+      </p>
+
+      <h3>Hello World</h3>
+      <p>Call the /hello endpoint on the .NET host.</p>
+      <div class="button-group">
+        <button class="btn" onclick="callHelloWorld()">
+          Call Hello World
+        </button>
+        <button class="btn btn-secondary" onclick="callHelloWorldWithName()">
+          Call with Name
+        </button>
+      </div>
+
+      <h3>Host Response</h3>
+      <div class="code-block" id="host-result">
+        Click a button above to test host communication.
+      </div>
+    </div>
+
+    <div class="section">
+      <h2>Host Status</h2>
+      <div class="info-row">
+        <span class="info-label">Host Port:</span>
+        <span class="info-value" id="host-port">Loading...</span>
+      </div>
+      <div class="info-row">
+        <span class="info-label">Host Available:</span>
+        <span class="info-value" id="host-available">Unknown</span>
+      </div>
+    </div>
+  </div>
+
   <!-- Logs Tab -->
   <div id="logs" class="tab-content">
     <div class="section">
@@ -558,6 +599,9 @@
     async function initializeView() {
       log('info', 'Demo view initialized');
 
+      // Update host status display
+      updateHostStatus();
+
       // Load addon data
       try {
         const data = await invokeAddon('getDemoData');
@@ -701,6 +745,66 @@
       }
     }
 
+    // ============================================================
+    // HOST DEMO FUNCTIONS
+    // ============================================================
+
+    async function callHelloWorld() {
+      const resultEl = document.getElementById('host-result');
+      resultEl.innerHTML = '<span class="loading"></span> Calling host...';
+      log('info', 'Calling host /hello endpoint');
+
+      try {
+        const result = await invokeAddon('callHelloWorld');
+        resultEl.textContent = JSON.stringify(result, null, 2);
+        if (result.error) {
+          log('error', `Host error: ${result.error}`);
+          document.getElementById('host-available').textContent = 'No (Error)';
+        } else {
+          log('info', `Host response: ${result.message}`);
+          document.getElementById('host-available').textContent = 'Yes';
+        }
+      } catch (err) {
+        resultEl.textContent = 'Error: ' + err.message;
+        log('error', `Host call failed: ${err.message}`);
+        document.getElementById('host-available').textContent = 'No (Exception)';
+      }
+    }
+
+    async function callHelloWorldWithName() {
+      const name = prompt('Enter your name:', 'World');
+      if (!name) return;
+
+      const resultEl = document.getElementById('host-result');
+      resultEl.innerHTML = '<span class="loading"></span> Calling host...';
+      log('info', `Calling host /hello/${name} endpoint`);
+
+      try {
+        const result = await invokeAddon('callHelloWorld', name);
+        resultEl.textContent = JSON.stringify(result, null, 2);
+        if (result.error) {
+          log('error', `Host error: ${result.error}`);
+        } else {
+          log('info', `Host response: ${result.message}`);
+        }
+      } catch (err) {
+        resultEl.textContent = 'Error: ' + err.message;
+        log('error', `Host call failed: ${err.message}`);
+      }
+    }
+
+    function updateHostStatus() {
+      // hostPort is received in addon:init-context
+      const portEl = document.getElementById('host-port');
+      if (hostPort) {
+        portEl.textContent = hostPort;
+        document.getElementById('host-available').textContent = 'Checking...';
+      } else {
+        portEl.textContent = 'Not available';
+        document.getElementById('host-available').textContent = 'No (No port)';
+      }
+    }
+
     // ============================================================
     // LOGGING
     // ============================================================