chore: scaffold tracks and tooling

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scala/test.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+# Usage: ./test.sh [MNN]   (no arg = all tests)
+set -euo pipefail
+cd "$(dirname "$0")"
+SCALA_CLI="${SCALA_CLI:-$(command -v scala-cli || echo "$HOME/.local/bin/scala-cli")}"
+if [ $# -ge 1 ]; then
+  exec "$SCALA_CLI" test src test project.scala -- "*$1*"
+else
+  exec "$SCALA_CLI" test src test project.scala
+fi