feat(parser): add PipeExpr grammar rules

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

src/parser/shrimp.grammar

@@ -53,6 +53,7 @@ item {
 
 
 consumeToTerminator {
+  PipeExpr |
   ambiguousFunctionCall |
   IfExpr |
   FunctionDef |
@@ -61,6 +62,14 @@ consumeToTerminator {
   expressionWithoutIdentifier
 }
 
+PipeExpr {
+  pipeOperand ("|" pipeOperand)+
+}
+
+pipeOperand {
+  FunctionCall | FunctionCallOrIdentifier
+}
+
 FunctionCallOrIdentifier {
   Identifier
 }