`wasm watch` fails to run carts unless they are named cart.wasm
### Description

If you happen to rename your cart from ``cart.wasm`` to ``my_zig_game.wasm``, then ``w4 watch zig-out/lib/my_zig_game.wasm`` will fail with a ENOENT error:

```
events.js:291
      throw er; // Unhandled 'error' event
      ^

Error: ENOENT: no such file or directory, open 'zig-out/lib/cart.wasm'
Emitted 'error' event on ReadStream instance at:
    at internal/fs/streams.js:136:12
    at FSReqCallback.oncomplete (fs.js:156:23) {
  errno: -2,
  code: 'ENOENT',
  syscall: 'open',
  path: 'zig-out/lib/cart.wasm'
}
```
That is: ``w4 watch`` seems to ignore the cart filename supplied as a command line argument.
``w4 run zig-out/lib/my_zig_game.wasm`` is working fine though.

### System info

- Os: Arch Linux
- Wasm-4 2.53, but I'm pretty sure I experienced it with an earlier 2.5 version during the jam
- Zig 0.9.1 - I don't think this is relevant. I don't know if this issue is specific to zig projects or if this happens with other languages

### How to replicate


```shell
#!/bin/sh

cd /tmp
rm -rf my_zig_game
w4 new --zig my_zig_game
(
  cd my_zig_game;
  sed -i -e 's/addSharedLibrary("cart"/addSharedLibrary("my_zig_game"/' build.zig
  zig build && \
  test -f zig-out/lib/my_zig_game.wasm && echo "zig-out/lib/my_zig_game.wasm does exist" && \
  w4 watch zig-out/lib/my_zig_game.wasm
)
```
