[tools] Replace APK utilities with skill file apps

.github/skills/extract-android-assemblies/SKILL.md

@@ -0,0 +1,35 @@
+---
+name: extract-android-assemblies
+description: Locally extract managed DLL files from .NET for Android APK, AAB, assembly-store, or compressed DLL inputs, including legacy/current store layouts and LZ4/Zstd compression. Use when investigating a customer Android package, getting assemblies for ILSpy or decompilation, unpacking assembly stores, or recovering ABI-specific managed files.
+---
+
+# Extract Android Assemblies
+
+Extract customer assemblies locally with the bundled C# file-based app. Never upload the input package or extracted code.
+
+## Workflow
+
+1. Resolve the input file and choose a new output directory. Keep temporary customer artifacts outside the repository.
+2. From the repository root, run:
+
+   ```text
+   dotnet run --file .github/skills/extract-android-assemblies/scripts/extract-android-assemblies.cs -- --output <output-directory> <input.apk-or-aab>
+   ```
+
+3. Pass multiple input files after the output option when needed.
+4. Do not reuse a non-empty output directory: the app refuses to overwrite files.
+5. Report:
+   - detected inputs
+   - extracted DLL count grouped by ABI
+   - whether LZ4 or Zstd decompression occurred
+   - the local output directory
+   - unsupported or corrupt store details
+
+The app supports:
+
+- legacy `assemblies/assemblies.blob` store sets and manifests
+- historical `libassemblies.{abi}.blob.so` stores
+- current `libassembly-store.so` stores
+- individual legacy and RID-specific packaged assemblies
+- raw, ELF `payload`, and `_assembly_store` symbol wrappers
+- uncompressed, `XALZ`/LZ4, and `XAZS`/Zstd assembly data