### Added

- `docs/UPSTREAM-SYNC.md` — the recurring upstream sync as a runbook: the
  standing resolutions, which side wins each and the issue that decided it
  (#200).

- It names the step the 0.6.0 sync nearly shipped without: auditing what the
  merge brought in that did **not** conflict. `git merge` asks no question
  about a function upstream added to a file this tree owns (#200).

- It records that the same mechanic applies to state, not just to call sites: a
  resolved region can silently remove a producer whose consumers auto-merged,
  and every one of those consumers degrades to empty rather than erroring
  (#200).

- It says to verify with the runner's tooling, because "green locally" was
  wrong three times in one sync — untracked files, a pinned linter, and a
  pinned `jq` whose empty-input exit code differs (#200).

- It says to test the merge RESULT when other PRs are open: Forgejo tests
  heads, so two green branches can produce a red tree (#200).

- `.upstream-ref` records the upstream commit this tree carries, in
  machine-readable form beside the CHANGELOG's prose (#200).

- `test/upstream-delta.test.sh` fails the PR that scatters forge branching into
  a file the inventory does not name — offline, and refusing rather than
  skipping when the recorded ref is missing (#200).

- `docs/CONSUMERS.md` states that two ceremonies answer to the same version
  number, and how a consumer says which one it pinned (#200).