skill: add Android skills

.agents/skills/r8-analyzer/references/REFLECTION-GUIDE.md

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+A categorized summary of the keep rule examples, including the code patterns to
+look for (imports/usage) and the corresponding suggested rules.
+
+### 1. Reflection: Classes Loaded by Name
+
+**Scenario:** A library or app loads a class dynamically using a string name
+
+- **Look for:**
+  `Class.forName("...")`,
+  `getDeclaredConstructor().newInstance()`, or interfaces used for dynamic loading.
+
+- **Example Code:**
+  `kotlin
+  val taskClass = Class.forName(className)
+  val task = taskClass.getDeclaredConstructor().newInstance() as StartupTask`
+
+- **Suggested Keep Rule:**
+  \`\`\`proguard
+
+  -keep class \* implements com.example.library.StartupTask {
+  (); } \`\`\`
+
+### 2. Reflection: Classes Passed using `::class.java`
+
+**Scenario:** An app passes a class reference directly to a library function.
+
+- **Look for:** `::class.java` (Kotlin) or `.class` (Java) passed as an argument.
+- **Example Code:**
+  `kotlin
+  fun <T> register(clazz: Class<T>) { }
+  // Usage:
+  register(MyService::class.java)`
+
+- **Suggested Keep Rule:**
+  \`\`\`proguard
+
+  # Keep the class itself (R8 usually handles this, but explicit rules ensure stability)
+
+  -keep class com.example.app.MyService {
+  (); } \`\`\`
+
+### 3. Annotation-Based Reflection (Methods/Classes)
+
+**Scenario:** Using custom annotations to mark methods or classes for reflective
+execution.
+
+**Look for:** Custom `@interface` definitions and `getDeclaredMethods()`
+filtered by annotation.
+**Example Code:**
+`kotlin
+annotation class ReflectiveExecutor
+// Logic: find methods annotated with @ReflectiveExecutor and invoke them`
+
+- **Suggested Keep Rule:** \`\`\`proguard # Keep the annotation itself -keep @interface com.example.library.ReflectiveExecutor
+
+# Keep members of any class annotated with this specific annotation
+-keepclassmembers class \* {
+@com.example.library.ReflectiveExecutor \*;
+}
+\`\`\`
+
+### 4. Optional Dependencies (Soft Dependencies)
+
+**Scenario:** A core library checks if an optional module is present in the
+classpath.
+
+- **Look for:** `try-catch` blocks around `Class.forName()` used to toggle features.
+- **Example Code:** \`\`\`kotlin private const val VIDEO_TRACKER_CLASS = "com.example.analytics.video.VideoEventTracker"
+
+try {
+Class.forName(VIDEO_TRACKER_CLASS).getDeclaredConstructor().newInstance()
+} catch (e: ClassNotFoundException) { /\* skip feature \*/ }
+\`\`\`
+
+- **Suggested Keep Rule:** `proguard
+  # Preserve the optional class so the check doesn't fail due to shrinking
+  -keep class com.example.analytics.video.VideoEventTracker {
+  <init>();
+  }`
+
+### 5. Accessing Private Members
+
+**Scenario:** Using reflection to access internal fields or methods not exposed
+with public APIs.
+
+- **Look for:** `getDeclaredField("...")` or `getDeclaredMethod("...")` followed by `isAccessible = true`.
+- **Example Code:**
+  `kotlin
+  val secretField = instance::class.java.getDeclaredField("secretMessage")
+  secretField.isAccessible = true`
+
+- **Suggested Keep Rule:**
+  \`\`\`proguard
+
+  # Specifically keep the private field/method by name and type
+
+  -keepclassmembers class com.example.LibraryClass {
+  private java.lang.String secretMessage;
+  }
+  \`\`\`
+
+### 6. Parcelable (Manual Implementation)
+
+**Scenario:** Implementing `Parcelable` without using the `@Parcelize`
+annotation.
+
+- **Look for:** `implements Parcelable` and a static `CREATOR` field.
+- **Example Code:**
+  `kotlin
+  class MyData : Parcelable {
+  // Manual implementation with CREATOR field
+  }`
+
+- **Suggested Keep Rule:**
+  *(Note: If using `import kotlinx.parcelize.Parcelize`, R8/ProGuard rules are
+  generated automatically. If manual, use the following:)*
+  `proguard
+  -keepclassmembers class * implements android.os.Parcelable {
+  static android.os.Parcelable$Creator CREATOR;
+  }`
+
+### 7. Enums and Obfuscation
+
+**Scenario:** App uses `Enum.valueOf("STRING_NAME")` indirectly (e.g.,using JSON
+deserialization) and the enum names get obfuscated.
+
+- **Look for:** Unnecessary generic Enum keep rules in ProGuard files.
+- **Example Code:**
+  \`\`\`proguard
+
+  # Unnecessary rule
+
+  -keepclassmembers enum \* { \*; }
+  \`\`\`
+- **Suggested Keep Rule:**
+  \*(Note: The default `proguard-android-optimize.txt` already contains the optimal
+  rules for Enums (keeping `values()` and `valueOf(String)`). Any additional
+  manual rules for Enums are redundant.) # No manual rule needed. Use default
+  proguard-android-optimize.txt.