Create copy-all button

[benwbrum]

We should add a feature that copies HTR text in bulk into the transcription screen, a bit similar to how Autolink applies links in bulk (without saving).

Implementation ideas:

• Strip ALTO to plaintext on the server side, using the same code we use for loading OCR text from files or IIIF manifests.
• Either render the plaintext in the form when the site loads or fetch it from a new controller action.
• Append the plaintext into the editor.

We can experiment with replacing bad readings through a cleanup (either dictionary or ChatGPT-based) with deletion/replacement of the conflicts to make it easier for users to find bad readings.

[benwbrum]

For user testing, we should explore the following variations:

• Copy all button vs. initial population (à la current OCR correction flow)
• Plaintext from ALTO vs. diff/normalized plaintext with place-holders to fix.