Add automatic PR validation workflow integrated with Zola deployment (#325)

This PR adds automatic build validation for pull requests to prevent
website deployment failures by integrating PR validation directly into
the existing Zola deployment workflow.

## Problem
Currently, PRs are not validated to ensure the website will render
correctly, which can result in deployment failures when changes are
merged to the main branch.

## Solution
Enhanced the existing `zola-deploy.yml` workflow to handle both PR
validation and production deployment:

- **Triggers on pull requests**: Added `pull_request` trigger targeting
the main branch for validation
- **Conditional deployment**: Uses `if: github.event_name !=
'pull_request'` to skip deployment steps for PRs
- **Smart checkout**: Automatically checks out PR branch for pull
requests or main branch for deployments
- **Unified build logic**: Both PR validation and deployment use
identical build processes

## Benefits
- **Prevents deployment failures**: Catches build issues before they
reach production
- **Immediate feedback**: Contributors get build validation results
directly in their PRs
- **Consistent validation**: Uses identical build logic as production
deployment
- **Reduced maintenance**: Single workflow file eliminates code
duplication
- **Minimal implementation**: Enhanced existing workflow instead of
adding separate files

The workflow validates:
- TOML configuration syntax errors
- Missing or broken content files
- Template rendering problems
- Sass compilation issues
- Any other build-time errors

This ensures that only PRs with valid, buildable changes can be merged,
significantly reducing the risk of deployment failures while maintaining
a clean, consolidated workflow structure.

Fixes #324.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>

Author: Copilot

.github/workflows/zola-deploy.yml

@@ -3,6 +3,8 @@ name: Deploy website
 on:
   push:
     branches: ["main"]
+  pull_request:
+    branches: ["main"]
   repository_dispatch:
     types: [deploy]
   workflow_dispatch:
@@ -16,10 +18,12 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - name: Checkout prod
+      - name: Checkout
         uses: actions/checkout@v4
         with:
-          ref: main
+          ref: >-
+            ${{ github.event_name == 'pull_request' &&
+                github.head_ref || 'main' }}
           path: website
 
       - name: Checkout valkey-doc
@@ -37,38 +41,45 @@ jobs:
       - name: Checkout valkey-bloom
         uses: actions/checkout@v4
         with:
-            repository: valkey-io/valkey-bloom
-            path: valkey-bloom
+          repository: valkey-io/valkey-bloom
+          path: valkey-bloom
 
       - name: Checkout valkey-search
         uses: actions/checkout@v4
         with:
-            repository: valkey-io/valkey-search
-            path: valkey-search
+          repository: valkey-io/valkey-search
+          path: valkey-search
 
       - name: Checkout valkey-json
         uses: actions/checkout@v4
         with:
-            repository: valkey-io/valkey-json
-            path: valkey-json
+          repository: valkey-io/valkey-json
+          path: valkey-json
 
       - name: Init commands, topics and clients
         run: |
           cd website
-          ./build/init-topics-and-clients.sh ../valkey-doc/topics ../valkey-doc/clients
-          ./build/init-commands.sh ../valkey-doc/commands ../valkey/src/commands ../valkey-bloom/src/commands ../valkey-json/src/commands ../valkey-search/src/commands
+          ./build/init-topics-and-clients.sh ../valkey-doc/topics \
+            ../valkey-doc/clients
+          ./build/init-commands.sh ../valkey-doc/commands \
+            ../valkey/src/commands ../valkey-bloom/src/commands \
+            ../valkey-json/src/commands ../valkey-search/src/commands
 
       - name: Build only
         uses: shalzz/zola-deploy-action@v0.19.1
         env:
           BUILD_DIR: website
           BUILD_ONLY: true
           BUILD_THEMES: false
+
       - name: Upload artifact
+        if: github.event_name != 'pull_request'
         uses: actions/upload-pages-artifact@v3
         with:
           path: ./website/public
+
   deploy:
+    if: github.event_name != 'pull_request'
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}