Drop apt, pull shellcheck from GitHub releases

act_runner's job containers live on a temporary bridge network that
does not inherit the runner's own egress path, so apt-get against
Canonical mirrors can time out even on a US host. Remove the apt step,
rely on the tools baked into gitea/runner-images, and fetch the
shellcheck static binary over HTTPS when it is missing.

Also add a short network diagnostics step to make future egress
issues obvious at a glance.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -45,53 +45,60 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Install toolchain (only what's missing)
+      - name: Network diagnostics
+        run: |
+          set +e
+          echo "=== DNS ==="
+          cat /etc/resolv.conf 2>/dev/null | head -5 || true
+          echo "=== Route ==="
+          ip route 2>/dev/null | head -3 || true
+          echo "=== Egress probe (5s connect timeout) ==="
+          for url in \
+            https://github.com \
+            https://objects.githubusercontent.com \
+            https://mirrors.aliyun.com \
+            http://archive.ubuntu.com \
+            http://security.ubuntu.com \
+          ; do
+            code=$(curl -sS -o /dev/null -w '%{http_code}' -m 5 --connect-timeout 5 "$url" || echo TIMEOUT)
+            printf '  %-45s -> %s\n' "$url" "$code"
+          done
+
+      - name: Ensure required tools (shellcheck via GitHub release)
         run: |
           set -euo pipefail
 
-          MISSING=()
-          for tool in shellcheck jq curl tar sha256sum; do
-            command -v "$tool" >/dev/null 2>&1 || MISSING+=("$tool")
+          # 镜像 gitea/runner-images:ubuntu-latest 已自带 curl / jq / tar / sha256sum。
+          # 唯一通常缺失的是 shellcheck，从 GitHub releases 拉静态二进制即可，不走 apt。
+          for tool in curl jq tar sha256sum; do
+            command -v "$tool" >/dev/null || {
+              echo "::error::基础工具 $tool 不在 PATH 中，镜像异常。请更换 runner 镜像。" >&2
+              exit 1
+            }
           done
 
-          if [[ ${#MISSING[@]} -eq 0 ]]; then
-            echo "所有工具已就绪，跳过安装。"
+          if command -v shellcheck >/dev/null 2>&1; then
+            echo "shellcheck 已就绪：$(shellcheck --version | awk '/^version:/{print $2}')"
             exit 0
           fi
-          echo "需要安装: ${MISSING[*]}"
 
+          SC_VER=v0.10.0
+          case "$(uname -m)" in
+            x86_64)  SC_ARCH=x86_64 ;;
+            aarch64) SC_ARCH=aarch64 ;;
+            *) echo "::error::不支持的架构: $(uname -m)" >&2; exit 1 ;;
+          esac
+          URL="https://github.com/koalaman/shellcheck/releases/download/${SC_VER}/shellcheck-${SC_VER}.linux.${SC_ARCH}.tar.xz"
+          echo "下载 $URL"
+          curl -fsSL --retry 3 --connect-timeout 15 -o /tmp/shellcheck.tar.xz "$URL"
+          tar -xJf /tmp/shellcheck.tar.xz -C /tmp
           if [[ $EUID -ne 0 ]] && command -v sudo >/dev/null 2>&1; then
             SUDO=sudo
           else
             SUDO=
           fi
-
-          # 切换到阿里云镜像以避开 archive.ubuntu.com / security.ubuntu.com 出境超时。
-          if [[ -f /etc/apt/sources.list.d/ubuntu.sources ]]; then
-            $SUDO sed -i \
-              -e 's|http://archive.ubuntu.com/ubuntu|https://mirrors.aliyun.com/ubuntu|g' \
-              -e 's|http://security.ubuntu.com/ubuntu|https://mirrors.aliyun.com/ubuntu|g' \
-              /etc/apt/sources.list.d/ubuntu.sources
-          fi
-          if [[ -f /etc/apt/sources.list ]]; then
-            $SUDO sed -i \
-              -e 's|http://archive.ubuntu.com/ubuntu|https://mirrors.aliyun.com/ubuntu|g' \
-              -e 's|http://security.ubuntu.com/ubuntu|https://mirrors.aliyun.com/ubuntu|g' \
-              /etc/apt/sources.list
-          fi
-
-          # 实际安装的包名映射（coreutils 提供 sha256sum）。
-          PKGS=()
-          for tool in "${MISSING[@]}"; do
-            case "$tool" in
-              sha256sum) PKGS+=(coreutils) ;;
-              *) PKGS+=("$tool") ;;
-            esac
-          done
-
-          $SUDO apt-get update -qq
-          DEBIAN_FRONTEND=noninteractive $SUDO apt-get install -y -qq --no-install-recommends \
-            "${PKGS[@]}" ca-certificates
+          $SUDO install -m 0755 "/tmp/shellcheck-${SC_VER}/shellcheck" /usr/local/bin/shellcheck
+          shellcheck --version | awk '/^version:/{print "shellcheck 已安装：" $2}'
 
       - name: Run shellcheck
         run: |