Clone the repo in CI without GitHub-hosted actions

Why: The runner cannot reach github.com, so cloning actions/checkout timed out before any test ran.
Evidence: mirrors.aliyun.com/golang/go1.27.1.linux-amd64.tar.gz returned HTTP 200. The workflow now fetches GITHUB_SHA with the job token and installs Go from that mirror.
Impact: Submodule checkout still requires SUBMODULE_TOKEN. A missing secret fails the job with that message.
Refs: feature/agent-stack-r0-r1
Co-authored-by: Cursor <cursoragent@cursor.com>

.gitea/workflows/ci.yml

@@ -10,14 +10,29 @@ jobs:
     env:
       GOPROXY: https://goproxy.cn,direct
     steps:
-      - name: Configure submodule auth over HTTPS
-        run: git config --global url."https://weichen:${{ secrets.SUBMODULE_TOKEN }}@git-home.u1680832.nyat.app:30319/".insteadOf "ssh://git@git-ssh.u1680832.nyat.app:31411/"
-      - uses: actions/checkout@v4
-        with:
-          submodules: recursive
-      - uses: actions/setup-go@v5
-        with:
-          go-version: "1.27"
+      - name: Checkout
+        env:
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          SUBMODULE_TOKEN: ${{ secrets.SUBMODULE_TOKEN }}
+        run: |
+          set -euo pipefail
+          git init -q
+          git remote add origin "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git"
+          git -c http.extraheader="AUTHORIZATION: token ${TOKEN}" fetch --depth=1 origin "${GITHUB_SHA}"
+          git checkout -q --detach FETCH_HEAD
+          if [ -z "${SUBMODULE_TOKEN}" ]; then
+            echo "SUBMODULE_TOKEN is not configured" >&2
+            exit 1
+          fi
+          git config --global url."https://weichen:${SUBMODULE_TOKEN}@git-home.u1680832.nyat.app:30319/".insteadOf "ssh://git@git-ssh.u1680832.nyat.app:31411/"
+          git -c fetch.recurseSubmodules=false submodule update --init --recursive
+      - name: Install Go 1.27.1
+        run: |
+          set -euo pipefail
+          curl -fsSL -o "$RUNNER_TEMP/go.tgz" https://mirrors.aliyun.com/golang/go1.27.1.linux-amd64.tar.gz
+          tar -C /usr/local -xzf "$RUNNER_TEMP/go.tgz"
+          ln -sfn /usr/local/go/bin/go /usr/local/bin/go
+          ln -sfn /usr/local/go/bin/gofmt /usr/local/bin/gofmt
       - name: Vet, test, and race
         run: GOWORK=off go vet ./... && GOWORK=off go test -count=1 ./... && GOWORK=off go test -count=1 -race ./...
   docker-checkout-hostgateway:
@@ -26,5 +41,13 @@ jobs:
     env:
       GITHUB_SERVER_URL: http://gitea:3000
     steps:
-      - uses: actions/checkout@v4
-      - run: test -f go.mod && echo "docker-mode checkout via host-gateway OK"
+      - name: Checkout without GitHub actions
+        env:
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set -euo pipefail
+          git init -q
+          git remote add origin "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git"
+          git -c http.extraheader="AUTHORIZATION: token ${TOKEN}" fetch --depth=1 origin "${GITHUB_SHA}"
+          git checkout -q --detach FETCH_HEAD
+          test -f go.mod && echo "docker-mode checkout via host-gateway OK"