We register buffers with language servers lazily when in multi-buffer
(when the excerpt is interacted with); this does not account for inlay
hints, of which a mere presence on a screen is enough to query a
language server with a path it does not recognize. This posed a problem
with typescript-language-server, which sent a notification to the user
whenever they had a multibuffer open with inlay hints enabled.

Closes #ISSUE

Release Notes:

- Fixed annoying pop-up with typescript-language-server that happened in
multi-buffers with inlay hints enabled.