fix: Skip PSScriptAnalyzer install on cache hit (#35)

The lint job was unconditionally running Install-Module even when the
module was already restored from cache. This caused Install-Module
-Force to conflict with the already-loaded cached module, triggering a
NullReferenceException in PSScriptAnalyzer.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tablackburn

.github/workflows/CI.yaml

@@ -18,6 +18,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Cache PowerShell modules
+        id: cache-lint-modules
         uses: actions/cache@v5
         with:
           path: ~/.local/share/powershell/Modules
@@ -26,6 +27,7 @@ jobs:
             ${{ runner.os }}-psmodules-lint-
 
       - name: Install PSScriptAnalyzer
+        if: steps.cache-lint-modules.outputs.cache-hit != 'true'
         shell: pwsh
         run: |
           Set-PSRepository -Name PSGallery -InstallationPolicy Trusted