Initial commit: Sizzletracker Android music tracker

A retro, grid-based music tracker for Android (Kotlin + Jetpack Compose,
single Activity) with four equally-capable input methods (touch, keyboard,
gamepad, MIDI) and four tabs: tracker, mixer, toolbox, settings.

Highlights:
- Tracker: Canvas-drawn 4-track pattern grid over an 8-lane arrangement roll,
  with a glyph cache and draw-phase state reads so the playhead and edits
  redraw without per-frame recomposition.
- Audio: sample-accurate sequencer feeding a shared AudioEngine, driven by
  either a Kotlin AudioTrack loop or native Oboe/AAudio via JNI (16 KB-aligned
  native libs). media3 MediaSession for lock-screen/headset transport.
- Toolbox: 16 instrument/effect slots with a 2-octave audition keyboard;
  single-tap select, double-tap edit, long-press clear.
- Note entry: long-press cell popups (piano keyboard / value steppers) plus
  keyboard/gamepad stepping that resumes from the last note/channel entered.
  Velocity capped at 0x7F, channel at 16.
- Selection/clipboard (cut/copy/paste/delete) and .sng import/export
  compatible with the reference desktop tool.
- A `profile` build type (non-debuggable, debug-signed) for realistic
  on-device performance testing.
- Developer handover documentation under docs/.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

gradle/libs.versions.toml

@@ -0,0 +1,45 @@
+# Gradle "version catalog". This single file is the ONE place where library
+# versions live. Instead of scattering version numbers across build files, code
+# refers to them by name, e.g. libs.androidx.core.ktx. Update a number here and
+# the whole project picks it up.
+
+[versions]
+agp = "8.5.2"                 # Android Gradle Plugin
+kotlin = "2.0.20"             # Kotlin language + compiler
+composeCompiler = "2.0.20"    # Compose compiler is now bundled with Kotlin plugin
+coreKtx = "1.13.1"
+lifecycle = "2.8.6"
+activityCompose = "1.9.2"
+composeBom = "2024.09.03"     # Bill Of Materials: pins all Compose libs together
+media3 = "1.4.1"              # MediaSession / background playback
+datastore = "1.1.1"          # Persisting settings/preferences
+coroutines = "1.9.0"
+
+[libraries]
+androidx-core-ktx = { module = "androidx.core:core-ktx", version.ref = "coreKtx" }
+androidx-lifecycle-runtime-ktx = { module = "androidx.lifecycle:lifecycle-runtime-ktx", version.ref = "lifecycle" }
+androidx-lifecycle-viewmodel-compose = { module = "androidx.lifecycle:lifecycle-viewmodel-compose", version.ref = "lifecycle" }
+androidx-activity-compose = { module = "androidx.activity:activity-compose", version.ref = "activityCompose" }
+
+# Compose — versions come from the BOM below, so no version.ref here.
+androidx-compose-bom = { module = "androidx.compose:compose-bom", version.ref = "composeBom" }
+androidx-compose-ui = { module = "androidx.compose.ui:ui" }
+androidx-compose-ui-graphics = { module = "androidx.compose.ui:ui-graphics" }
+androidx-compose-ui-tooling = { module = "androidx.compose.ui:ui-tooling" }
+androidx-compose-ui-tooling-preview = { module = "androidx.compose.ui:ui-tooling-preview" }
+androidx-compose-foundation = { module = "androidx.compose.foundation:foundation" }
+androidx-compose-material3 = { module = "androidx.compose.material3:material3" }
+androidx-compose-material-icons-extended = { module = "androidx.compose.material:material-icons-extended" }
+
+# Background playback + media notification controls
+androidx-media3-session = { module = "androidx.media3:media3-session", version.ref = "media3" }
+androidx-media3-common = { module = "androidx.media3:media3-common", version.ref = "media3" }
+
+androidx-datastore-preferences = { module = "androidx.datastore:datastore-preferences", version.ref = "datastore" }
+
+kotlinx-coroutines-android = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-android", version.ref = "coroutines" }
+
+[plugins]
+android-application = { id = "com.android.application", version.ref = "agp" }
+kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
+kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "composeCompiler" }

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists