feat(app): event line provides entire line contents as a single event; add(event): .cancel event

Introduce `.cancel` event that is fired when the user sends EOF
in *non raw mode* renderings. The event `.line` now sends the
entire line (even if larger than the internal buffer) but requires
now an `Allocator`.

examples/direct.zig

@@ -77,7 +77,7 @@ pub fn main() !void {
 
     const gpa = allocator.allocator();
 
-    var app: App = .init(.{}, .{});
+    var app: App = .init(gpa, .{}, .{});
     var renderer = zterm.Renderer.Direct.init(gpa);
     defer renderer.deinit();
 
@@ -147,9 +147,10 @@ pub fn main() !void {
 
             // pre event handling
             switch (event) {
-                // NOTE maybe I want to decouple the `key`s from the user input too? i.e. this only makes sense if the output is not echoed!
-                // otherwise just use gnu's `readline`?
+                // NOTE draw the character with the ctrl indication and a newline to make sure the rendering stays consistent
+                .cancel => try renderer.writeCtrlDWithNewline(),
                 .line => |line| {
+                    defer gpa.free(line);
                     log.debug("{s}", .{line});
                 },
                 // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback