ci(windows-installer): keep installer artifacts 1 and 7 days, not 90

The unsigned installer is only needed while SignPath fetches it and the
signed one is attached to the release, but both were kept for the default
90 days on every tag, daily builds included, which filled the account's
Actions storage.

.github/workflows/windows-installer.yml

@@ -118,6 +118,9 @@ jobs:
           name: bambuddy-windows-installer-unsigned
           path: installers/windows/build/output/*.exe
           if-no-files-found: error
+          # Only needed while SignPath fetches it during this run; the default
+          # 90 days of every daily build filled the account's Actions storage.
+          retention-days: 1
 
   publish:
     needs: build
@@ -235,6 +238,9 @@ jobs:
           name: bambuddy-windows-installer
           path: installers/windows/build/output/*.exe
           if-no-files-found: error
+          # Release tags attach the installer to the release below; the run
+          # copy is only for downloading a manual or daily build.
+          retention-days: 7
 
       - name: Attach installer to release
         if: startsWith(github.ref, 'refs/tags/v')