Fix release publishing and add a CI token fallback

Tag builds since v0.2.2 built all artifacts but never published a release:
- tools/publish_release.sh only assembled AUTH in the GITEA_TOKEN branch; the
  ~/.git-credentials branch set CRED and then used an unbound ${AUTH[@]} under
  `set -u`, so every API call failed and the job ended "could not create or find
  release". It now sets AUTH=(-u "$CRED").
- The repo has no GITEA_TOKEN secret and the runner has no git credentials, so the
  workflow now falls back to the built-in workflow token:
  GITEA_TOKEN: ${{ secrets.GITEA_TOKEN || github.token }}.

v0.2.9 was then built and published locally with all five artifacts (portable
Linux/Windows/macOS, NSIS installer, AppImage) and the release page verified via
the API. v0.2.4-v0.2.8 remain unpublished; they are superseded by the latest.

Docs
- docs/RELEASING.md records the incident and the local-publish fallback.
- TODO gains a release-pipeline follow-up (verify CI on the next tag).
- MEMORY notes the root cause, the missing secret, and which releases exist.
- Version 0.2.10.

tools/publish_release.sh

@@ -28,6 +28,9 @@ for l in open(os.path.expanduser('~/.git-credentials')):
     echo "error: no credentials for $HOST in ~/.git-credentials" >&2
     exit 1
   fi
+  # curl basic auth. (Previously only CRED was set, so ${AUTH[@]} was unbound
+  # under `set -u` and every API call failed silently.)
+  AUTH=(-u "$CRED")
 else
   echo "error: set GITEA_TOKEN or provide ~/.git-credentials" >&2
   exit 1