restructure: move el compiler content into lang/

lang/tests/calendar/examples/rhythm-cycle-30hr.el

@@ -0,0 +1,18 @@
+// rhythm-cycle-30hr.el — rhythm_cycle_phase(0.5) under CycleCalendar(30.hours)
+// returns the next instant at the 15-hour mark of the cycle.
+
+fn run_test() -> Int {
+    let period: Duration = 30.hours
+    let cal: Calendar = cycle_calendar(period)
+    let r: Rhythm = rhythm_cycle_phase(0.5)
+    let base: Instant = unix_seconds(0)
+    let next: Instant = rhythm_next_after(r, base, cal)
+    let elapsed_ns: Duration = next - base
+    let elapsed_secs: Int = duration_to_seconds(elapsed_ns)
+    // 15 hours = 54000 seconds.
+    return elapsed_secs
+}
+
+fn main() -> Void {
+    println(int_to_str(run_test()))
+}