grammar: introduce bitwise ops & shifts; retire legacy >> ARROW

- Tokenizer: add tokens for << >> & | ^ (SHIFT_LEFT/RIGHT, BIT_AND/OR/XOR); keep ||, &&, |>
- Parser: precedence layers for bit ops (| ^ &) and shift (<< >>); remove >> Arrow production
- AST: add BitAnd/BitOr/BitXor/Shr with Display
- MIR builder: map bit ops and Shr to MIR BinaryOp
- Interpreter: implement integer-only bit ops and shifts, mask shift count to 0..63

Compatibility: legacy >> Arrow removed from parser; use |> for pipeline.

src/ast.rs

@@ -333,7 +333,11 @@ pub enum BinaryOperator {
     Multiply,
     Divide,
     Modulo,
+    BitAnd,
+    BitOr,
+    BitXor,
     Shl,      // << shift-left (Phase 1)
+    Shr,
     Equal,
     NotEqual,
     Less,
@@ -362,7 +366,11 @@ impl fmt::Display for BinaryOperator {
             BinaryOperator::Multiply => "*",
             BinaryOperator::Divide => "/",
             BinaryOperator::Modulo => "%",
+            BinaryOperator::BitAnd => "&",
+            BinaryOperator::BitOr => "|",
+            BinaryOperator::BitXor => "^",
             BinaryOperator::Shl => "<<",
+            BinaryOperator::Shr => ">>",
             BinaryOperator::Equal => "==",
             BinaryOperator::NotEqual => "!=",
             BinaryOperator::Less => "<",