Quiet the Update Book progress dialog: bar and explanation only (BL-16893)

[JohnThomson]

Problem

"Update Book" (Collections tab), and since BL-16852 the automatic page update that runs before the AI image editor opens or after a page-size change, show a progress dialog that fills with a running log: a line per stage ("Updating collection settings...", "Gathering Data...", "Updating pages...") and two lines per image ("Reading metadata from X", "Writing metadata to HTML for X"), plus "Preparing image: X" for every oversized picture. A 40-image book scrolls through some 80 lines that only repeat what the percent bar already shows, and bury the one sentence that explains why the dialog appeared.

Cause

Those lines are IProgress.WriteStatus calls dating from 2012. They were harmless while every caller showed status in a single overwriting WinForms label. BL-16870 (2026-09-14) moved Update Book onto the React progress dialog through WebProgressAdapter, whose WriteStatus appends a permanent line, and BL-16852 made the same pass run automatically.

What the PR does

• Adds QuietStatusProgress, an IProgress wrapper that drops status lines and forwards everything else: messages, warnings, errors and the percent.
• BookProcessor.ProcessBook, which both dialogs run, wraps the progress it is given in it for the whole run. Update Book now shows just its title and the moving bar; the automatic update shows its one explanatory sentence and the bar. Any warning or error still appears.
• Book hands the two per-image passes (mirroring image metadata into the HTML, shrinking oversized images) the same wrapper, so the other callers of bringing a book up to date (importing a .bloomSource, Update All Books) keep their stage lines but lose the line per image.
• The Copyright and License dialog's "add this information to all images" is untouched: it runs a WinForms dialog with one overwriting status line, where naming each file as it goes is useful.
• Tests cover the wrapper, the quiet bring-up-to-date path, and the still-verbose whole-book metadata path. A stale comment about who passes a real progress to the image-shrink migration is corrected.

Ref: https://issues.bloomlibrary.org/youtrack/issue/BL-16893

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Devin review

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This change is 

[JohnThomson]

[Claude Fable 5.1] Consulted Devin on 2026-09-18 up to commit 919c326 (one review round, on the first push).

Devin raised no bugs and no flags on this PR, and no Informational items. Its overview describes the change the same way the PR description does. CI (pr-automation) passed; no other review bot posted.