view: duplicated Wasm in the site, extra LSP notifications and copied doc strings

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Found in the review of #2057, which adds the experimental view. Paths refer to #2059's head.

Summary

Wasm shipped twice. The site carries the 5.9 MB engine both as site/playground/pkg and as site/view/pkg (just copies the playground's build for the view).
Notifications for unseen documents. A client that opts in to graphcal/viewModelDidChange gets one after every analysis of every document, including documents no view shows.
Copied doc strings. Each IR stage and each instance copies a declaration's doc string; Arc<str> would share it.