Skip user input on duplicate import decisions when files match exactly

### Problem

I have a hunch that once tagged, the conflicting files were crc32-exact duplicates of each other. I have seen multiple Beets questions about importing a duplicate album that matches in all listed attributes. Both of these were imported through Beets, I think I just had two copies of them on my hard drive. If the crc32s match, the files are literally identical and Beets can safely just delete one and keep the other without bothering the user.

```
E:\Music\Paul McCarney (15 items)
Correcting tags from:
Paul McCarney - Run Devil Run
To:
Paul McCartney - Run Devil Run
URL:
https://musicbrainz.org/release/066e963b-2838-37df-a606-b0129a86a053
(Similarity: 99.4%) (artist) (CD, 1999, US, Capitol Records)
* Try Not To Cry -> Try Not to Cry
* Shake A Hand -> Shake a Hand
This album is already in the library!
Old: 15 items, MP3, 320kbps, 40:46, 93.4 MiB
New: 15 items, MP3, 320kbps, 40:46, 93.4 MiB
```

The issue names no files, tests, or entry points; start by tracing the duplicate-album import decision and the CRC32 comparison that precedes the user prompt. The exact-match case should retain one copy, delete the other, and complete without asking for input, while other conflicts still prompt the user.

Written by the indexing model from the issue text.