M0: toolchain, monorepo scaffold, gateway plugin skeleton, CMP app

- gateway-plugin/: android platform plugin (plugin.yaml + adapter.py
  register(ctx) + no-op AndroidAdapter) + stub modules for M1-M5
- app/: Compose Multiplatform project (shared KMP + androidApp +
  desktopApp) with Gradle wrapper; builds :androidApp:assembleDebug
  and :desktopApp:compileKotlin
- scripts/guard_hermes_agent.sh + pre-commit hook: fail if hermes-agent/
  is staged (read-only reference, never committed)
- .gitignore excludes hermes-agent/; docs/ reference library

app/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+    kotlin("multiplatform") version "2.1.0" apply false
+    kotlin("android") version "2.1.0" apply false
+    kotlin("jvm") version "2.1.0" apply false
+    id("com.android.application") version "8.7.3" apply false
+    id("com.android.library") version "8.7.3" apply false
+    id("org.jetbrains.compose") version "1.7.3" apply false
+    id("org.jetbrains.kotlin.plugin.compose") version "2.1.0" apply false
+}
+
+tasks.register("clean") {
+    delete(rootProject.layout.buildDirectory)
+}