docs: cut GitHub releases so the push mirror cannot delete them

GitHub is a pruning push mirror of Gitea, so a tag created by
"gh release create" belongs to no upstream ref and disappears on the next
synchronisation, orphaning the release and its archives. Document the order
that survives it: push the tag to Gitea, wait for the mirror, verify the tag
on GitHub, publish with --verify-tag.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/CHANGELOG.md

@@ -71,6 +71,13 @@ dragged.**
   authentication and takes the job with it, leaving a published release with no
   assets. The Project Layout section is gone — it duplicated ARCHITECTURE's
   package map and had drifted out of date.
+- **Cutting a GitHub release now documents the push mirror it has to survive.**
+  GitHub is a pruning push mirror of Gitea, so `gh release create` creating the
+  tag itself produces a tag Gitea does not know about, which the next
+  synchronisation deletes — orphaning the release and taking its uploaded
+  archives with it, without a single failed step to point at. The procedure is
+  push the tag to Gitea, wait for the mirror, verify the tag on GitHub, then
+  publish with `--verify-tag`.
 - **`docs/TESTS.md`** matches the suite it indexes again. It listed 130 tests
   against 170 in the tree, omitted four test files entirely, and named two tests
   that no longer exist. Every test function now appears exactly once, under the

docs/DEVELOPMENT.md

@@ -19,6 +19,7 @@ Toolchain, dependency, build, and release information for contributors.
    - [Packaging](#packaging)
 6. [CI](#6-ci)
    - [Cutting a release](#cutting-a-release)
+   - [Releasing through the GitHub push mirror](#releasing-through-the-github-push-mirror)
 
 ## 1. Technology Stack and Tools
 
@@ -289,12 +290,19 @@ Before tagging:
    `main`, so the tag lands on a commit the forge actually has.
 
 Then create and publish a release with a matching `v` tag on the forge (GitHub
-Releases / Codeberg releases). You can do that from the web UI or the CLI, e.g.:
+Releases / Codeberg releases). `origin` is the Gitea repository, and GitHub is a
+push mirror of it, so the tag is pushed to Gitea and reaches GitHub through the
+mirror — never created on GitHub directly (see
+[Releasing through the GitHub push mirror](#releasing-through-the-github-push-mirror)):
 
 ```bash
 git tag v0.11.5
-git push origin v0.11.5   # and to the Codeberg remote
+git push origin v0.11.5   # Gitea; and to the Codeberg remote
-gh release create v0.11.5 --generate-notes   # GitHub; publishes the release
+
+# wait for the mirror, then confirm GitHub actually has the tag
+git ls-remote --tags https://github.com/mixeme/gosentry.git v0.11.5
+
+gh release create v0.11.5 --verify-tag --generate-notes   # GitHub; publishes the release
 ```
 
 Publishing the release triggers the workflow: it strips the leading `v` from
@@ -309,3 +317,35 @@ succeed, but the upload step fails on authentication and takes the job down with
 it, leaving a published release with no attached assets. GitHub needs no such
 setup: `softprops/action-gh-release` falls back to the built-in `GITHUB_TOKEN`,
 and the workflow already grants it `contents: write`.
+
+### Releasing through the GitHub push mirror
+
+The GitHub repository `mixeme/gosentry` is not a separate remote you push to; it
+is a push mirror driven by Gitea. Gitea mirrors with pruning, so every ref that
+exists on GitHub but not in Gitea is deleted on the next synchronisation.
+
+This is what breaks the obvious way of cutting a GitHub release. `gh release
+create v1.0.0` creates the tag on GitHub when it is missing — a tag Gitea has
+never heard of. The next mirror run prunes it, GitHub orphans the release whose
+tag disappeared and turns it into a draft, and the release looks deleted on the
+Releases page. The archives go with it. Nothing reports an error: the workflow
+ran, the assets uploaded, and the release evaporated afterwards.
+
+The order that works is therefore:
+
+1. `git push origin <tag>` — the tag enters Gitea, which owns it.
+2. Wait for the mirror, or force it with **Settings → Repository → Mirror
+   Settings → Synchronize Now** in Gitea.
+3. `git ls-remote --tags https://github.com/mixeme/gosentry.git <tag>` — confirm
+   GitHub has it.
+4. `gh release create <tag> --verify-tag …` — `--verify-tag` is the guard, not a
+   nicety: without it `gh` silently creates the doomed tag when the mirror has
+   not caught up yet.
+
+Release notes and assets are GitHub-side metadata; a mirror push cannot touch
+them, so once the release sits on a mirrored tag, later synchronisations leave
+it alone. Two consequences follow. Moving a published tag in Gitea force-pushes
+it on GitHub and leaves the release pointing at a different commit, and deleting
+a published tag in Gitea destroys the GitHub release along with its uploaded
+archives — neither is recoverable from the mirror side. Codeberg is unaffected:
+its releases live in the same forge as its tags.