#1050 Add a redundancy rule to the lede-voice doctrine

[williamthorsen]

What

The changelog-voice doctrine gains a third drafting rule that aims to reduce verbosity by eliminating statements containing trivial or redundant information. The drafting checklist and the automated draft audit now screen for it too, and the audit gains the cross-sentence comparison it previously could not make.

Why

The doctrine's outcome test and identifier ban both pass sentences that add nothing new: an obvious corollary of the change, a "nothing else broke" reassurance no one asked for, or a restatement of an earlier sentence. That padding recurred across changelog and PR ledes, and in the reassurance case planted doubt the reader never had, with no rule positioned to catch it.

Details

🎉 Features

• Rule 3 (redundancy ban) is added as a peer of the outcome test and identifier ban, covering the self-evident corollary, the harm-avoided guarantee, and the cross-sentence paraphrase, and extending the deletion test across sentences.
• The drafting checklist gains the rule and a matching cross-sentence audit step.
• The changelog-writer subagent's audit now compares sentences to one another and to the change's own implication, and its output format carries a Rule 3 failure line.

♻️ Refactoring

• Rule references throughout the doctrine and its two consumers are decoupled from a hard-coded count, so a future rule no longer forces a lockstep sweep of "two rules" / "all three" phrasing.
• Redundant illustrations are trimmed from the doctrine: a duplicate corollary example, an over-explained guarantee bullet, and two example blocks that no longer earned their space.

Closes #1050

[github-actions]

Dependency audit

Production dependency audit passed.