docs: explain the Phase 0 git history normalization

Public-facing transparency artifact for the 2026-05-13 git-history
rewrite. Plain-language explanation of: what changed (uniform author
metadata to canonical operator identity + Co-authored-by trailers
preserving AI involvement), why (LLC ownership transfer to certctl LLC
+ pre-traction cleanup), what is preserved (archive tag +
off-platform bundle), how to recover a stale clone, and the operational
note that external PRs aren't accepted until a CLA workflow is set up.

The README pointer to this doc is intentionally omitted — the page is
discoverable via grep against the repo (`history-normalization`),
via the next CHANGELOG entry, and via any forensic observer who
notices the rewrite and grep-searches for an explanation.

Closes the public-transparency leg of Phase 0 (Path B2, Pattern C).

docs/history-normalization.md

@@ -0,0 +1,99 @@
+# Git history normalization — 2026-05-13
+
+> Last reviewed: 2026-05-13
+
+This page documents a one-time normalization of certctl's git history
+that landed on `master` on 2026-05-13. If you are reading this because
+your clone failed to fast-forward, or because a commit SHA you bookmarked
+no longer resolves, this is the explanation.
+
+## What changed
+
+Every commit's `author` and `committer` metadata was rewritten to a
+single canonical identity (`shankar0123 <skreddy040@gmail.com>`). Where
+the original author was an AI/automation identity (Claude, Copilot,
+cowork agent, certctl-bot, etc.), a `Co-authored-by:` trailer was
+appended to the commit message preserving the original identity. The
+intent is a uniform single-author authorship layer + preserved
+attribution of AI involvement.
+
+No source-code content was changed by the rewrite. Every line of code
+in every commit is byte-for-byte identical to its pre-rewrite version.
+Only `author` / `committer` metadata and (for ~129 AI-touched commits)
+a `Co-authored-by:` trailer line were touched.
+
+## Why
+
+Two reasons:
+
+1. **LLC ownership transfer.** The codebase is now legally owned by
+   **certctl LLC**, which the operator incorporated to hold rights in
+   the project. The BSL 1.1 Licensor field in `LICENSE` flipped from a
+   natural-person name to `certctl LLC` in the same change set. Uniform
+   per-commit authorship under one canonical operator identity makes
+   the chain of title between the codebase and the LLC unambiguous.
+
+2. **Pre-traction cleanup.** The rewrite cost of git-history
+   normalization scales with how many external clones and references
+   have calcified against specific commit SHAs. Doing it now, before
+   the project has a large external surface, minimizes disruption to
+   downstream consumers.
+
+## What is preserved
+
+The exact pre-rewrite history is preserved on origin at the tag
+**`archive/pre-author-normalization-2026-05-13`**. If you need to
+reference an original commit SHA from before the rewrite — for example
+in a blog post, an external citation, or a pre-rewrite release artifact
+— check that tag. The tag is immutable; we will not move or delete it.
+
+A separate off-platform bundle backup of the pre-rewrite tree is also
+held by the operator (off-repo, not pushed). Both artifacts ensure the
+original history is recoverable forever.
+
+## Recovering after the rewrite
+
+If you had a clone of certctl from before 2026-05-13, your local
+history diverged from origin's at the rewrite. Easiest recovery:
+
+```bash
+cd certctl
+git fetch origin
+git fetch origin --tags
+git reset --hard origin/master
+```
+
+This force-aligns your local tree with the new origin. Any local
+branches you had based on pre-rewrite history will need rebasing onto
+the new master.
+
+If you want to inspect the pre-rewrite state for any reason:
+
+```bash
+git fetch origin archive/pre-author-normalization-2026-05-13
+git checkout archive/pre-author-normalization-2026-05-13
+```
+
+## Container images and release tarballs
+
+ghcr.io container images that were published before the rewrite
+(`ghcr.io/certctl-io/certctl-{server,agent}:<old-tag>`) remain pullable
+indefinitely. Their OCI source-SHA labels reference commit SHAs that
+now only resolve via the `archive/` tag — the images themselves still
+work; only the source-SHA back-reference points at the archive. New
+release images published after the rewrite reference current SHAs
+normally.
+
+If you downloaded a release tarball before the rewrite, the tarball's
+contents are unchanged; only its associated `git` SHA differs from the
+current `v2.x.y` tag (which has been re-pointed to the rewritten
+commit at the same logical point in history).
+
+## Operational note for contributors
+
+Future contributions to certctl should be authored under the
+operator's canonical git identity. Pull requests from external
+contributors will need a Contributor License Agreement (CLA) workflow,
+which the project will set up before accepting external PRs. Until
+then, the project does not solicit or accept external code
+contributions.