feat: Implement Pipeline support

Adds support for pipelines, allowing streams to be chained together and
transformed.
This includes new types for `PipeStream` and `SourceAdapter`, along with
modifications
to the `Environment` to manage pipeline execution. A new example
`pipeline.myc`
demonstrates its usage.

src/ast/types.rs

@@ -592,7 +592,15 @@ impl fmt::Display for Value {
             }
             Value::FieldAccessor(k) => write!(f, ".{}", k.name()),
             Value::Function(f_meta) => write!(f, "<native fn, {:?}>", f_meta.purity),
-            Value::Object(o) => write!(f, "<{}>", o.type_name()),
+            Value::Object(o) => {
+                if let Some(pipe) = o.as_any().downcast_ref::<crate::ast::rtl::streams::PipelineNode>() {
+                    write!(f, "PipelineNode[last: {:?}]", pipe.series.get_item(0))
+                } else if let Some(val_series) = o.as_any().downcast_ref::<crate::ast::rtl::series::SharedValueSeries>() {
+                    write!(f, "SharedValueSeries[len: {}]", val_series.buffer.borrow().len())
+                } else {
+                    write!(f, "<{}>", o.type_name())
+                }
+            }
             Value::Cell(c) => write!(f, "{}", c.borrow()),
             Value::TailCallRequest(_) => write!(f, "<tail call request>"),
         }