Check out the sibling repos the proxy's path dependencies need

The first CI run built OpenSSL fine and then failed: Cargo.toml depends on
../continuum-schemas and ../continuum-common, which the runner's checkout
of the proxy alone did not have.

.gitea/workflows/discover-windows.yml

@@ -42,9 +42,29 @@ jobs:
     defaults:
       run:
         shell: powershell
+        # Every `run` step below works in the proxy's checkout.
+        working-directory: continuum-proxy
     timeout-minutes: 90
     steps:
+      # Cargo.toml has path dependencies on two sibling repositories
+      # (`../continuum-schemas`, `../continuum-common`), so all three are laid
+      # out side by side inside the workspace - the checkout action will not
+      # place a repo outside it, which is why the proxy is in a subdirectory
+      # rather than at the root. The siblings are taken from the same branch
+      # name as this one: the proxy's code needs their unreleased commits.
       - uses: actions/checkout@v4
+        with:
+          path: continuum-proxy
+      - uses: actions/checkout@v4
+        with:
+          repository: Continuum/continuum-schemas
+          ref: ${{ github.ref_name }}
+          path: continuum-schemas
+      - uses: actions/checkout@v4
+        with:
+          repository: Continuum/continuum-common
+          ref: ${{ github.ref_name }}
+          path: continuum-common
 
       - name: Install the Rust MSVC toolchain
         shell: powershell
@@ -132,7 +152,7 @@ jobs:
         uses: actions/upload-artifact@v3
         with:
           name: continuum-discover-printers-windows
-          path: dist/*
+          path: continuum-proxy/dist/*
           if-no-files-found: error
 
       # After the upload on purpose: the executable is useful even if a test