fix: use podman containers for checkout on minimal host runner

Host runner lacks git and node. Fetch repo archive via wget in
alpine container, then run lint/link-check against extracted files.
Single-line commands to avoid multiline escaping issues.

.gitea/workflows/ci.yml

@@ -11,29 +11,16 @@ jobs:
     runs-on: linux
     steps:
       - name: Checkout
-        run: |
-          git clone --depth 1 --branch "${{ github.ref_name }}" \
-            "${{ github.server_url }}/${{ github.repository }}.git" workspace
+        run: podman run --rm -v "$PWD:/out:Z" docker.io/library/alpine:3 sh -c "wget -qO- '${{ github.server_url }}/${{ github.repository }}/archive/${{ github.ref_name }}.tar.gz' | tar xz -C /out --strip-components=1"
 
       - name: Markdown lint
-        run: |
-          podman run --rm \
-            -v "$PWD/workspace:/work:Z" \
-            docker.io/davidanson/markdownlint-cli2:v0.17.2 \
-            "**/*.md"
+        run: podman run --rm -v "$PWD:/work:Z" docker.io/davidanson/markdownlint-cli2:v0.17.2 "**/*.md"
 
   link-check:
     runs-on: linux
     steps:
       - name: Checkout
-        run: |
-          git clone --depth 1 --branch "${{ github.ref_name }}" \
-            "${{ github.server_url }}/${{ github.repository }}.git" workspace
+        run: podman run --rm -v "$PWD:/out:Z" docker.io/library/alpine:3 sh -c "wget -qO- '${{ github.server_url }}/${{ github.repository }}/archive/${{ github.ref_name }}.tar.gz' | tar xz -C /out --strip-components=1"
 
       - name: Check internal links
-        run: |
-          podman run --rm \
-            -v "$PWD/workspace:/work:Z" \
-            -w /work \
-            docker.io/library/python:3.12-slim \
-            python3 scripts/check-links.py
+        run: podman run --rm -v "$PWD:/work:Z" -w /work docker.io/library/python:3.12-slim python3 scripts/check-links.py