CI: JS-action-free workflow (host runner needs no Node)

actions/checkout is a JavaScript action; a host-mode act_runner needs
 on PATH to run it, which the AGP box doesn't have. Replace it with
a plain git fetch from the local Gitea using the injected ${{ github.token }}.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015jtxAiu5dAW4WxCNdGkrkJ

.gitea/workflows/checkpoint.yml

@@ -3,11 +3,10 @@ name: checkpoint
 # Runs the full checkpoint suite (migrations, backend pytest, Godot smoke
 # tests, multiplayer, fresh-clone boot) on every push and PR.
 #
-# Requires a Gitea Actions runner (act_runner) with:
+# Runs on a `host`-label act_runner on the AGP box: Docker, ~/godot/godot,
-#   - Docker access (the suite starts an ephemeral Postgres via docker compose)
+# and Python 3 are already there. Deliberately uses no JavaScript actions
-#   - the Godot 4.6.2 headless binary at $HOME/godot/godot (or `godot` on PATH)
+# (actions/checkout etc.) so the host needs no Node install -- checkout is a
-#   - the backend Python deps installed (backend/requirements.txt)
+# plain git clone from the local Gitea. See docs/ci.md.
-# A `host`-label runner on the AGP box already has all of this. See docs/ci.md.
 
 on:
   push:
@@ -18,10 +17,19 @@ jobs:
   checkpoint:
     runs-on: host
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout
+        run: |
+          set -eu
+          rm -rf repo && mkdir repo && cd repo
+          git init -q
+          git remote add origin "http://x:${{ github.token }}@localhost:3000/${{ github.repository }}.git"
+          git fetch -q --depth 1 origin "${{ github.sha }}"
+          git checkout -q FETCH_HEAD
 
       - name: Backend deps
-        run: python -m pip install -r backend/requirements.txt
+        working-directory: repo
+        run: python3 -m pip install --quiet -r backend/requirements.txt
 
       - name: Checkpoint suite
-        run: python scripts/run_checkpoint_tests.py --postgres-port 25690 --backend-port 18690
+        working-directory: repo
+        run: python3 scripts/run_checkpoint_tests.py --postgres-port 25690 --backend-port 18690