docs: close out 260904 repository hygiene campaign - #3408

Summary

• Preserve the 12 local documentation commits that record the 260904 repository hygiene campaign.
• Add the final campaign plan, audit records, branch and PR drawdown ledgers, issue verdicts, and contributor-credit verification.
• Update CREDITS.md with the verified attribution gap.

Verification

• git status --short --branch — clean before push.
• git diff --stat origin/dev...HEAD — 15 documentation files, 870 insertions.
• No GUI or runtime behavior changed; the full test suite was not run for this docs-only change.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

Summary by CodeRabbit

• Documentation
  • Added comprehensive records for a repository hygiene campaign, including branch cleanup, pull request and issue reviews, validation procedures, audit results, and final outcomes.
  • Documented safeguards for preserving protected, active, and referenced work while identifying removable branches and superseded contributions.
  • Added guidance for accurately crediting carried contributions using GitHub-linked author identities.
  • Recorded attribution verification findings, including correction of a contributor credit before merge.
  • Added campaign verdicts, consolidation decisions, follow-up actions, and closeout metrics.