Introduce RecordingOpen viewer event

[jprochazk]

def event_handler(event):
  if event.type == "recording_open":
    print(recording_id)

viewer = Viewer()
viewer.on_event(event_handler)

[github-actions]

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Result	Commit	Link
✅	593f2c7	https://landing-54twfc0je-rerun.vercel.app/docs

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[github-actions]

Web viewer built successfully. If applicable, you should also test it:

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Result	Commit	Link	Manifest
✅	593f2c7	https://rerun.io/viewer/pr/10654	+nightly +main

^{Note: This comment is updated whenever you push a commit.}

[jprochazk]

Before, this was firing off the event twice... Which is really strange. I didn't investigate too deeply, I changed it to check not only that it's a SetStoreInfo message, but also that the store actually doesn't exist yet. That fixed it for me. I assume the root cause is that we are sending multiple store info messages somewhere.

[Wumpf]

huh, that's a bit worrisome 🤔
but your check makes sense regardless

[Wumpf]

seems low risk enough to add it to 0.24 last minute. Liking the doc strings very much, thanks!