fix: add manual trigger and branch specification for execution workflow

- Add workflow_dispatch for manual testing
- Specify branches for workflow_run trigger
- Helps ensure execution workflow can be triggered on revamp branch

Author: guchenhe

.github/workflows/sync_docs_execute.yml

@@ -5,6 +5,13 @@ on:
     workflows: ["Analyze Documentation Changes"]
     types:
       - completed
+    branches: [main, revamp]
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: 'PR number to process'
+        required: true
+        type: string
 
 permissions:
   contents: write