Update WP version and make schema inspector non-blocking

Bump the WordPress version in the setup step from 6.8 to 6.9. Add comments and set 'continue-on-error: true' for the schema inspector step to ensure schema changes do not block CI, as they are expected between WordPress versions.

Author: josephfusco

.github/workflows/schema-linter.yml

@@ -39,7 +39,7 @@ jobs:
       - name: Setup WordPress
         uses: ./.github/actions/setup-wordpress
         with:
-          wp-version: '6.8'
+          wp-version: '6.9'
 
       - name: Setup GraphQL Schema Linter
         run: npm install -g graphql-schema-linter@^3.0 graphql@^16
@@ -79,7 +79,11 @@ jobs:
           name: schema.graphql
           path: /tmp/schema.graphql
 
+      # Schema changes between WordPress versions are expected and not regressions in this plugin.
+      # The inspector runs to document changes for release notes, but doesn't block CI.
+      # Update wp-version above when releasing a new version with updated "Tested up to:" header.
       - name: Run Schema Inspector
+        continue-on-error: true
         run: |
           # This schema and previous release schema
           node_modules/.bin/graphql-inspector diff /tmp/${{ steps.get-latest-tag.outputs.tag }}.graphql /tmp/schema.graphql