Stable type identifiers: a missing piece for crABI and export

The fact that the network layer uses serialization actually expands the use case you already acknowledged; it doesn't restrict it. Regarding plugins, not all of them require an ABI; those based on WASM, IPC, or explicit serialization do not need one. And the Bevy issue wasn’t closed because the problem went away: cart closed it because they settled for TypePath as a workaround, explicitly acknowledging that the language doesn’t provide the right tool for this.