Versioned dependencies (via `--dep`) are not found

I have the following WAC document:

```
package root:component-val@0.0.1 targets fermyon:spin/http-trigger@2.0.0;

let c = new root:component { ... };

export c...;
```

I resolve it like so:

```
wac resolve aaugh.wac --registry wa.dev --dep "root:component=./target/wasm32-wasi/release/calculator_spin.wasm"
```

And life is good. But if I change root:component to have a version:

```
package root:component-val@0.0.1 targets fermyon:spin/http-trigger@2.0.0;

let c = new root:component@0.0.1 { ... };

export c...;
```

and invoke with the version:

```
wac resolve aaugh.wac --registry wa.dev --dep "root:component@0.0.1=./target/wasm32-wasi/release/calculator_spin.wasm"
```

I get:

```
error: failed to resolve document

× package `root:component` does not exist in the registry
╭─[aaugh.wac:3:13]
2 │
3 │ let c = new root:component@0.0.1 { ... };
· ──────────┬─────────
· ╰── package `root:component` does not exist
4 │
╰────
```

(If I revert the command line to the unversioned, uh, version, same error.)

Is this behaviour intentional? If so, could the error indicate more specifically what the user should do to fix it?