app: App streams should be distinct-until-changed based on state

In `packages/modules/app/src/app/App.ts`, there's a TODO noting that the public streams (`manifest$`, `config$`, etc.) should only emit when the underlying state actually changes:

```ts
// TODO make streams distinct until changed from state
```

Apply a `distinctUntilChanged` (or similar) comparison based on state to avoid redundant emissions.

Start in packages/modules/app/src/app/App.ts and inspect the TODO alongside the public stream definitions and their underlying state. Verify that manifest$, config$, and the other public streams emit only when their state changes, then run the app module's available tests to confirm redundant emissions are removed.

Written by the indexing model from the issue text.