refactor: zigify imports and usages

examples/demo.zig

@@ -7,7 +7,7 @@ const QuitText = struct {
 
     pub fn content(ctx: *anyopaque, cells: []zterm.Cell, size: zterm.Point) !void {
         _ = ctx;
-        std.debug.assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
 
         const y = 2;
         const x = size.x / 2 -| (text.len / 2);
@@ -191,6 +191,7 @@ pub fn main() !void {
 const log = std.log.scoped(.default);
 
 const std = @import("std");
+const assert = std.debug.assert;
 const zterm = @import("zterm");
 const input = zterm.input;
 const App = zterm.App(union(enum) {});