mod: replace Layout.content with Layout.render

The App.Renderer is used for the new `Layout.render` method. Each layout
renders itself now with corresponding renderers which might only update
parts of the screen, etc.

src/terminal.zig

@@ -62,6 +62,12 @@ pub fn write(buf: []const u8) !usize {
     return try std.posix.write(std.posix.STDIN_FILENO, buf);
 }
 
+pub fn setCursorPosition(pos: Position) !void {
+    var buf: [64]u8 = undefined;
+    const value = try std.fmt.bufPrint(&buf, "\x1b[{d};{d}H", .{ pos.row, pos.col });
+    _ = try std.posix.write(std.posix.STDIN_FILENO, value);
+}
+
 pub fn getCursorPosition() !Position {
     // Needs Raw mode (no wait for \n) to work properly cause
     // control sequence will not be written without it.