Initial public release.

subapp-sample/README.md

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+# KTag Sample Subapp
+
+A minimal Jetpack Compose subapp template for creating new KTag applications.
+
+## Overview
+
+The Sample subapp provides a starting point for creating new subapps in the KTag ecosystem. It demonstrates the minimal required structure and can be copied as a template for new functionality.
+
+## Architecture
+
+The simplest possible subapp structure:
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                   SampleActivity                        │
+│                  (Compose Host)                         │
+│  • Single "Hello World" screen                          │
+└─────────────────────────────────────────────────────────┘
+```
+
+## File Structure
+
+```
+src/main/java/club/clubk/ktag/apps/sample/
+├── SampleActivity.kt       # Main activity with Compose UI
+├── SampleSubApp.kt         # Subapp registration
+└── SampleInitializer.kt    # Startup initializer
+```
+
+## Creating a New Subapp
+
+To create a new subapp based on this template:
+
+1. **Copy the module**: Duplicate `subapp-sample` directory
+2. **Rename the package**: Update package name in all files
+3. **Update build.gradle.kts**: Change namespace
+4. **Register the subapp**: Update `SampleSubApp` with new ID, name, icon
+5. **Add to settings.gradle.kts**: Include new module
+6. **Add dependency**: Include in main app's dependencies
+
+## Required Components
+
+### SubApp Interface
+
+Every subapp must implement the `SubApp` interface:
+
+```kotlin
+class MySubApp : SubApp {
+    override val id = "myapp"           // Unique identifier
+    override val name = "My App"        // Display name
+    override val icon = R.drawable.ic_myapp  // Launcher icon
+
+    override fun createIntent(context: Context): Intent {
+        return Intent(context, MyActivity::class.java)
+    }
+}
+```
+
+### Initializer
+
+Register the subapp at startup:
+
+```kotlin
+class MyInitializer : Initializer<Unit> {
+    override fun create(context: Context) {
+        SubAppRegistry.register(MySubApp())
+    }
+
+    override fun dependencies(): List<Class<out Initializer<*>>> = emptyList()
+}
+```
+
+### AndroidManifest.xml
+
+Declare the activity and initializer:
+
+```xml
+<activity android:name=".MyActivity" android:exported="false" />
+
+<provider
+    android:name="androidx.startup.InitializationProvider"
+    android:authorities="${applicationId}.androidx-startup">
+    <meta-data
+        android:name=".MyInitializer"
+        android:value="androidx.startup" />
+</provider>
+```
+
+## Optional Features
+
+For more complex subapps, consider adding:
+
+| Feature | Reference |
+|---------|-----------|
+| Settings | See `subapp-koth` or `subapp-medic` |
+| MQTT | Implement `SettingsSubApp` interface |
+| BLE | See `subapp-bletool` or `subapp-koth` |
+| USB Serial | See `subapp-terminal` |
+| ViewModel | See `subapp-koth` or `subapp-medic` |
+
+## Dependencies
+
+- Jetpack Compose (Material3)
+- AndroidX Startup (for initialization)