fix(release): mount host Go into RPM container instead of downloading

go.mod specifies 'go 1.26' (no patch), making the download URL
go1.26.linux-amd64.tar.gz which 404s. Use actions/setup-go on the
runner and bind-mount GOROOT into the rockylinux container read-only,
removing the curl+tar download entirely.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -162,12 +162,16 @@ jobs:
         with:
           fetch-depth: 0
 
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
       - name: Build RPM
         run: |
           set -euo pipefail
           VERSION="${{ github.event.inputs.tag || github.ref_name }}"
           PKGVER="${VERSION#v}"
-          GO_VER="$(awk '/^go / { print $2; exit }' go.mod)"
+          GO_ROOT="$(go env GOROOT)"
 
           git archive --format=tar.gz --prefix=pgtidy-${PKGVER}/ HEAD \
             > pgtidy-${PKGVER}.tar.gz
@@ -177,15 +181,14 @@ jobs:
           mkdir -p rpm-out
           docker run --rm \
             -v "$(pwd):/build" \
-            -e GO_VER="${GO_VER}" \
+            -v "${GO_ROOT}:/usr/local/go:ro" \
             -e PKGVER="${PKGVER}" \
             -w /build \
             rockylinux:9 \
             bash -lc "
               set -euo pipefail
-              dnf install -y rpm-build git &&
-              curl -fsSL https://go.dev/dl/go\${GO_VER}.linux-amd64.tar.gz | tar -C /usr/local -xz &&
               export PATH=\$PATH:/usr/local/go/bin &&
+              dnf install -y rpm-build git &&
               mkdir -p ~/rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS} &&
               cp pgtidy-${PKGVER}.tar.gz ~/rpmbuild/SOURCES/ &&
               cp linux/centos/pgtidy.spec ~/rpmbuild/SPECS/ &&