ci: reuse existing REGISTRY_TOKEN secret for package publish

The repo already has a write:package REGISTRY_TOKEN secret (used by docker.yml).
Reuse it for uv publish instead of requiring new GITEA_PACKAGE_* secrets:
authenticate as GITHUB_ACTOR with the token as password. Update packaging docs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/publish.yml

@@ -2,8 +2,9 @@ name: publish
 
 # Build the Python package with uv and publish it to the self-hosted Gitea PyPI
 # registry on a version tag. Gated on lint + tests so a release can never ship
-# red. Publishing uses least-privilege Gitea Actions secrets; if they are absent
-# the job fails loudly instead of publishing anonymously.
+# red. Publishing reuses the existing REGISTRY_TOKEN package secret (the same one
+# docker.yml uses to push images); if it is absent the job fails loudly instead
+# of publishing anonymously.
 on:
   push:
     tags:
@@ -73,12 +74,11 @@ jobs:
       - name: Require publish credentials
         shell: bash
         env:
-          GITEA_PACKAGE_USER: ${{ secrets.GITEA_PACKAGE_USER }}
-          GITEA_PACKAGE_TOKEN: ${{ secrets.GITEA_PACKAGE_TOKEN }}
+          REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
         run: |
-          if [ -z "${GITEA_PACKAGE_USER}" ] || [ -z "${GITEA_PACKAGE_TOKEN}" ]; then
-            echo "::error::GITEA_PACKAGE_USER / GITEA_PACKAGE_TOKEN secrets are not set." >&2
-            echo "Configure a least-privilege PAT with write:package as Actions secrets." >&2
+          if [ -z "${REGISTRY_TOKEN}" ]; then
+            echo "::error::REGISTRY_TOKEN secret is not set." >&2
+            echo "Configure a PAT with write:package as the REGISTRY_TOKEN Actions secret." >&2
             exit 1
           fi
 
@@ -95,13 +95,15 @@ jobs:
       - name: Publish to Gitea PyPI registry
         shell: bash
         env:
-          GITEA_PACKAGE_USER: ${{ secrets.GITEA_PACKAGE_USER }}
-          GITEA_PACKAGE_TOKEN: ${{ secrets.GITEA_PACKAGE_TOKEN }}
+          # Reuse the existing package secret (same one docker.yml uses). The
+          # token authenticates as its owning Gitea user, so GITHUB_ACTOR is the
+          # username and the token is the password.
+          REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
         run: |
           uv publish \
             --publish-url https://git.hiddenden.cafe/api/packages/Hiddenden/pypi \
-            --username "${GITEA_PACKAGE_USER}" \
-            --password "${GITEA_PACKAGE_TOKEN}"
+            --username "${GITHUB_ACTOR}" \
+            --password "${REGISTRY_TOKEN}"
 
       # Optional second step to also publish to public PyPI lives behind its own
       # secret. Intentionally left as a disabled stub — this pass does NOT push