- 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.
- Tokenizer: add SHIFT_LEFT for '<<' (before <= detection)
- Parser: introduce parse_shift() layer; left-associative; only '<<' handled in Phase 1
- AST: add BinaryOperator::Shl and display
- MIR builder: map Shl -> BinaryOp::Shl
- Interpreter: implement Shl in both execution paths (integer-only, type error otherwise)
No change to '>>' (legacy ARROW remains). No runtime gate yet for SHL as it does not collide with existing syntax.
