Publish release candidates to a testing apt distribution

Pre-releases (versions with a hyphen) now upload their .debs to the
"testing" distribution instead of "stable", so servers following stable
never get an RC from apt upgrade. An RC can take its release notes from
its final version's section or Unreleased; the workflow checks the notes
with 'gitea-release.sh notes'. Also fix publishing RCs, whose .deb names
carry the Debian version (0.2.0~rc.1) and were rejected.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -2,7 +2,9 @@
 # is pushed:
 #   * a Gitea release with the CHANGELOG notes, the linux tarballs, the CLI
 #     for Linux, macOS and Windows, the .debs and SHA256SUMS;
-#   * the .debs (amd64, arm64) in the owner's Debian package registry.
+#   * the .debs (amd64, arm64) in the owner's Debian package registry:
+#     distribution "stable", or "testing" for a pre-release (a version
+#     with a hyphen), which Gitea also marks as a pre-release.
 #
 # Needs a repository secret RELEASE_TOKEN: an access token of a user who
 # can write to the repository, with the write:repository and write:package
@@ -30,8 +32,10 @@ jobs:
             echo "::error::tag $GITHUB_REF_NAME does not match VERSION ($version)"
             exit 1
           fi
-          if ! grep -q "^## \[$version\]" CHANGELOG.md; then
-            echo "::error::CHANGELOG.md has no '## [$version]' section"
+          # The release notes (a pre-release may use its final version's
+          # section or Unreleased; see scripts/gitea-release.sh).
+          if ! scripts/gitea-release.sh notes > /dev/null; then
+            echo "::error::no release notes for $version in CHANGELOG.md"
             exit 1
           fi