fix(ci): warn loudly when the Flatpak remote publish skips (#961)

The credential gate silently skipped the remote publish when
FLATPAK_GPG_PRIVATE_KEY / FLATPAK_REPO_TOKEN were unset, so the
documented auto-update remote could stay unpublished for releases at a
time (#951). Emit an Actions warning annotation and a run-summary entry
instead of a plain log line, and note in docs/FLATPAK_REMOTE.md that any
token with Contents write on the remote repo works.

Co-authored-by: Jatin K Malik <jatinkrmalik@gmail.com>

.github/workflows/release.yml

@@ -567,7 +567,8 @@ jobs:
       group: flatpak-remote
     steps:
       # Same pattern as publish-aur: an unconfigured remote skips the publish
-      # instead of failing the release.
+      # instead of failing the release. The skip is loud — a quiet one let the
+      # documented remote sit unpublished for releases at a time (#951).
       - name: Check remote credentials
         id: creds
         env:
@@ -576,7 +577,13 @@ jobs:
         run: |
           if [ -z "$FLATPAK_GPG_PRIVATE_KEY" ] || [ -z "$FLATPAK_REPO_TOKEN" ]; then
             echo "configured=false" >> "$GITHUB_OUTPUT"
-            echo "FLATPAK_GPG_PRIVATE_KEY and/or FLATPAK_REPO_TOKEN not set; skipping remote publish (docs/FLATPAK_REMOTE.md)"
+            msg="FLATPAK_GPG_PRIVATE_KEY and/or FLATPAK_REPO_TOKEN not set; skipping remote publish — the documented auto-update remote will not carry this release (docs/FLATPAK_REMOTE.md)"
+            echo "::warning::$msg"
+            {
+              echo "### :warning: Flatpak remote publish skipped"
+              echo
+              echo "$msg"
+            } >> "$GITHUB_STEP_SUMMARY"
           else
             echo "configured=true" >> "$GITHUB_OUTPUT"
           fi