feat: add enum path expression support in codegen

- Support ekPath in lowerExpr for enum variants (Color::Red → Color_Red)
- Support module paths (Std::Io::PrintLine → Std_Io_PrintLine)
- Add enums.bux example demonstrating enum usage
- Enums now compile and run correctly

examples/enums.bux

@@ -0,0 +1,34 @@
+// Enums - Enumeration types
+extern func Std_Io_PrintLine(s: String);
+extern func Std_Io_PrintInt(n: int);
+
+enum Color {
+    Red,
+    Green,
+    Blue
+}
+
+func ColorName(c: Color) -> String {
+    if c == Color::Red {
+        return "Red";
+    }
+    if c == Color::Green {
+        return "Green";
+    }
+    if c == Color::Blue {
+        return "Blue";
+    }
+    return "Unknown";
+}
+
+func Main() -> int {
+    let myColor: Color = Color::Green;
+    
+    Std_Io_PrintLine("My color is:");
+    Std_Io_PrintLine(ColorName(myColor));
+    Std_Io_PrintLine("Color value:");
+    Std_Io_PrintInt(myColor as int);
+    Std_Io_PrintLine("");
+    
+    return 0;
+}

src/hir_lower.nim

@@ -127,6 +127,12 @@ proc lowerExpr(ctx: var LowerCtx, expr: Expr): HirNode =
   of ekIdent:
     return hirVar(expr.exprIdent, typ, loc)
 
+  of ekPath:
+    # Handle enum variants: Color::Red → Color_Red
+    # or module paths: Std::Io::PrintLine → Std_Io_PrintLine
+    let mangledName = expr.exprPath.join("_")
+    return hirVar(mangledName, typ, loc)
+
   of ekSelf:
     return hirSelf(typ, loc)