Revert "ci: skip engine dispatch for site-only changes"

This reverts commit 465a34a.

Author: Seungpyo1007

.github/workflows/request-engine-pr-validation.yml

@@ -1,13 +1,21 @@
 name: request-engine-pr-validation
 
-# Ask TechEngine to validate TechAPI data and validator PRs. Homepage-only
-# changes are built and deployed by TechAPI itself; dispatching them to the
-# engine adds an unrelated checkout/cache dependency to a site review.
+# Ask TechEngine to validate TechAPI PRs and report the result back as PR
+# comments. Data changes get engine data checks; homepage changes get the
+# TechAPI site build check without moving PR ownership away from the human
+# author.
 on:
   pull_request:
     types: [opened, synchronize, reopened, ready_for_review]
     paths:
       - "data/**"
+      - "site/public/v1/**"
+      - "site/public/openapi.json"
+      - "site/src/**"
+      - "site/public/**"
+      - "site/astro.config.*"
+      - "site/package.json"
+      - "site/package-lock.json"
       - "app/validate.py"
       - "app/verify/**"
   workflow_dispatch: