Add cache status indicator to Spack CI

Shows whether dependencies are cached or need to be built:
- Cache hit: Lists already-installed packages (~5-10 min total)
- Cache miss: Warns about long build time (~30-40 min)

Helps users understand CI timing at a glance.

Author: sbryngelson

.github/workflows/spack.yml

@@ -146,6 +146,7 @@ jobs:
           spack config add "packages:all:target:[x86_64]"
 
       - name: Cache Spack Dependencies
+        id: spack-cache
         uses: actions/cache@v4
         with:
           path: |
@@ -155,6 +156,16 @@ jobs:
           restore-keys: |
             spack-deps-${{ runner.os }}-
 
+      - name: Check Cache Status
+        run: |
+          if [ "${{ steps.spack-cache.outputs.cache-hit }}" == "true" ]; then
+            echo "✓ Cache hit! Dependencies already built."
+            . spack/share/spack/setup-env.sh
+            spack find
+          else
+            echo "⚠ Cache miss. Will build dependencies from source (~30-40 min)."
+          fi
+
       - name: Install Package into Spack
         run: |
           . spack/share/spack/setup-env.sh