[vishr]

What this changes

An editorial pass over onebox.run's documentation, from a site-wide review against Diátaxis and a writing-style checklist. URLs, slugs and code examples are unchanged.

• Removes contrasts and closing lines that restated the sentence before them, slogans, provenance narration in generated pages, and many prose em dashes.
• States repeated claims once on the page that owns them and links from the others: the guarantees Onebox does not make, rollback versus data recovery, refused image guessing, and error codes as a contract.
• The upgrade guide puts its steps before the background; install explains the Buildx --format probe once; "A operator" and one agreement error are fixed.
• Generated text is changed in cmd/ob-docgen and regenerated. The drivers page now links PostgreSQL protection to the backups guide's "Declaring is not enabling" section.

Why this is correct

• just check passes, including the docgen check, site build, canonical and docs-URL checks.
• lychee over the built site: 3,647 links and anchors, 0 errors.
• Inline code spans compared before and after every edited page: only single removals where duplicate text was cut, none added.
• A Codex adversarial review checked that removed or reworded claims are still stated and still match the code; its one finding (the backup enablement link) is fixed here.

Effect on the safety envelope

None. Documentation wording only.

Checklist

• just check passes locally.
• Tests cover the new behaviour, including the failure paths (no behaviour change).
• Generated documentation is current (just check verifies this).
• I have accepted the CLA, or will when the bot asks on my first pull request.