ci: remove GitHub CI — native git.hanzo.ai + cd.hanzo.ai only

This workflow ran on a self-hosted actions-runner-controller pool. ARC is
decommissioned: CI executes inside git.hanzo.ai (Gitea Actions, .hanzo/workflows)
and delivery is cd.hanzo.ai reconciling the reviewed image pin in
hanzoai/universe. GitHub is a mirror and runs nothing.

Removed rather than repointed — there is no GitHub-side pool to move to, and
leaving it would keep ARC load-bearing.

.github/workflows/release.yml

@@ -1,52 +0,0 @@
-name: Release
-
-on:
-  push:
-    tags:
-      - 'v*'
-
-permissions:
-  contents: write
-  packages: write
-
-jobs:
-  release:
-    runs-on: hanzo-build-linux-amd64
-    steps:
-      - uses: actions/checkout@v4
-
-      - uses: actions/setup-go@v5
-        with:
-          go-version: '1.26.4'
-
-      - name: Build CLI binaries
-        run: |
-          VERSION=${GITHUB_REF_NAME#v}
-          mkdir -p cli/build
-
-          for pair in "linux/amd64" "linux/arm64" "darwin/amd64" "darwin/arm64"; do
-            OS=${pair%/*}
-            ARCH=${pair#*/}
-            OUTPUT="cli/build/migrate.${OS}-${ARCH}"
-            echo "Building $OUTPUT..."
-            CGO_ENABLED=0 GOOS=$OS GOARCH=$ARCH \
-              go build -a -o "$OUTPUT" \
-              -ldflags="-s -w -X main.Version=$VERSION" \
-              -tags 'datastore file' \
-              ./cmd/migrate
-            ln -f "$OUTPUT" cli/build/migrate
-            tar czf "${OUTPUT}.tar.gz" -C cli/build migrate
-          done
-
-          cd cli/build && sha256sum *.tar.gz > sha256sum.txt
-
-      - name: Create GitHub Release
-        env:
-          GH_TOKEN: ${{ github.token }}
-        run: |
-          gh release create ${{ github.ref_name }} \
-            cli/build/*.tar.gz \
-            cli/build/sha256sum.txt \
-            --title "${{ github.ref_name }}" \
-            --generate-notes \
-            --latest