ci: drop working-directory, cd into /src/_src explicitly

forgejo-runner v13 does not interpolate ${{ runner.workspace }}
in working-directory: (or ignores the field entirely for docker
containers), so the container tried to chdir to '/_src' (literally)
which does not exist.

The image WORKDIR is /src, so clone directly into /src/_src and cd
into it at the start of each step. Adds an echo of the checkout
SHA + branch state for visibility in the log.

.forgejo/workflows/buildAndTest.yml

@@ -42,7 +42,7 @@ jobs:
     steps:
     - name: Clone yavsc
       run: |
-        cd "$RUNNER_WORKSPACE"
+        cd /src
         git clone https://forgejo.pschneider.fr/notazof/yavsc.git _src
         cd _src
         if [ -n "${GITHUB_REF:-}" ]; then
@@ -50,12 +50,10 @@ jobs:
           git checkout FETCH_HEAD
         fi
         git submodule update --init --recursive --depth 1
+        echo "Checked out at $(git rev-parse HEAD) on $(git branch --show-current 2>/dev/null || echo detached HEAD)"
     - name: Restore dependencies
-      working-directory: ${{ runner.workspace }}/_src
-      run: dotnet restore
+      run: cd /src/_src && dotnet restore
     - name: Build
-      working-directory: ${{ runner.workspace }}/_src
-      run: dotnet build --no-restore
+      run: cd /src/_src && dotnet build --no-restore
     - name: Test
-      working-directory: ${{ runner.workspace }}/_src
-      run: dotnet test --no-build --verbosity normal
+      run: cd /src/_src && dotnet test --no-build --verbosity normal