feat: centralize release script and simplify workflow input

Move release.ps1 into the platform kit as the shared source of truth and remove include_readme_md input so all skills always publish readme_md by default.

.github/workflows/reusable-release-skill.yaml

@@ -11,10 +11,6 @@ on:
         required: false
         type: string
         default: windows.x86_64
-      include_readme_md:
-        required: false
-        type: boolean
-        default: false
       upload_url:
         required: false
         type: string
@@ -49,15 +45,12 @@ jobs:
 
       - name: Parse Metadata and Pack
         id: build_task
-        env:
-          INCLUDE_README_MD: ${{ inputs.include_readme_md }}
         run: |
           python -c "
           import frontmatter, os, json, shutil
           post = frontmatter.load('SKILL.md')
           metadata = dict(post.metadata or {})
-          if os.environ.get('INCLUDE_README_MD', 'false').lower() == 'true':
-              metadata['readme_md'] = (post.content or '').strip()
+          metadata['readme_md'] = (post.content or '').strip()
           openclaw_meta = metadata.get('metadata', {}).get('openclaw', {})
           slug = (openclaw_meta.get('slug') or metadata.get('slug') or metadata.get('name') or '').strip()
           if not slug: