Implement binary operations (BinOp) support
**Parser changes (parser.py):**
- Added ast.BinOp handling in _transform_expr()
- Emits: {type: "binop", left: ..., op: "Add|Sub|Mult|Div|Mod", right: ...}
**Codegen changes (llvm_codegen_signals.py):**
- Added BinOp handling in _emit_expr()
- Maps Python ops to LLVM instructions:
- Add → add i32
- Sub → sub i32
- Mult → mul i32
- Div → sdiv i32 (signed division)
- Mod → srem i32 (signed remainder)
**Result:**
Before: count = count + 1 → store i32 0 (WRONG!)
After: count = count + 1 → load, add i32 1, store ✓
**Still TODO:**
The counter buttons now UPDATE the signal correctly, but the display
doesn't update because f-string text nodes aren't reactive yet.
We need reactive text nodes (similar to reactive attributes).
All 55 tests passing ✓
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Aaron SinclairandClaude
e1219ea0c1