refactor(docs): shorten Core-flow filename, add mermaid support, translate english version

- Rename Core-execution-flow.md to Core-flow.md (short filename)
- Install @docusaurus/theme-mermaid and enable mermaid in config
- Translate english Core-flow.md from Chinese to English
- Fix TOC anchor IDs for English version

Co-Authored-By: Claude <noreply@anthropic.com>

Author: JusterZhu

website/docs/doc/Core-execution-flow.md website/docs/doc/Core-flow.mdwebsite/docs/doc/Core-execution-flow.md renamed to website/docs/doc/Core-flow.md

@@ -62,6 +62,12 @@ const config = {
     ],
   ],
 
+  markdown: {
+    mermaid: true,
+  },
+
+  themes: ['@docusaurus/theme-mermaid'],
+
   themeConfig:
     /** @type {import('@docusaurus/preset-classic').ThemeConfig} */
     ({