v0.6.0 — JavaScript Compute Engine

Author the compute layer in JavaScript by setting engine: javascript.

--- compute ---
function transform(df) {
  df.addColumn('Tax', r => r.Revenue * 0.2);
  return df;
}

• Runs in a Node vm subprocess sandbox via JSON-over-stdio bridge
• Curated globals: Math, JSON, Number, String, Array, Object, Date, Map, Set, Promise, Error
• Blocked: require, process, fs, child_process, Buffer, setTimeout
• --max-old-space-size=256, per-stage VM timeout, total wall-clock cap
• df helpers: col, sum, mean, max, min, where, addColumn, columns, shape
• Falls back gracefully via JsRuntimeUnavailable when Node missing
• 48 new tests including sandbox bypass attempts

See spec/SPEC.md §19.