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>

ritz/llvm_codegen_signals.py

@@ -1093,6 +1093,25 @@ class SignalLLVMIRGenerator:
             result_var = self._new_var()
             self.lines.append(f"  %{result_var} = select i1 %{cond_var}, i32 {true_val}, i32 {false_val}")
             return f"%{result_var}"
+        elif expr["type"] == "binop":
+            # Handle binary operations (e.g., count + 1, x - 5)
+            left_val = self._emit_expr(expr["left"])
+            right_val = self._emit_expr(expr["right"])
+            op = expr["op"]
+
+            # Map Python operators to LLVM instructions
+            op_map = {
+                "Add": "add",
+                "Sub": "sub",
+                "Mult": "mul",
+                "Div": "sdiv",  # signed division
+                "Mod": "srem",  # signed remainder
+            }
+
+            llvm_op = op_map.get(op, "add")
+            result_var = self._new_var()
+            self.lines.append(f"  %{result_var} = {llvm_op} i32 {left_val}, {right_val}")
+            return f"%{result_var}"
         else:
             # Unknown expression type
             return "0"

ritz/parser.py

@@ -356,6 +356,14 @@ def _transform_expr(expr: ast.expr | None) -> dict[str, Any]:
             "body": _transform_expr(expr.body),
             "orelse": _transform_expr(expr.orelse),
         }
+    elif isinstance(expr, ast.BinOp):
+        # Handle binary operations (e.g., count + 1, x - 5, a * b)
+        return {
+            "type": "binop",
+            "left": _transform_expr(expr.left),
+            "op": type(expr.op).__name__,  # Add, Sub, Mult, Div, Mod, etc.
+            "right": _transform_expr(expr.right),
+        }
     else:
         return {"type": "unknown", "ast_type": type(expr).__name__}