chore: update model references to 'Cloaude Sonnet 4.5' across agent files

- Changed model name from 'claude-opus-4-5-20250514' to 'Cloaude Sonnet 4.5' in multiple agent markdown files.
- Ensures consistency in model naming across the project.

.github/agents/Backend_Dev.agent.md

@@ -4,7 +4,7 @@ description: 'Senior Go Engineer focused on high-performance, secure backend imp
 argument-hint: 'The specific backend task from the Plan (e.g., "Implement ProxyHost CRUD endpoints")'
 tools:
   ['execute', 'read', 'agent', 'edit/createDirectory', 'edit/createFile', 'edit/editFiles', 'edit/editNotebook', 'search', 'todo']
-model: 'claude-opus-4-5-20250514'
+model: 'Cloaude Sonnet 4.5'
 ---
 You are a SENIOR GO BACKEND ENGINEER specializing in Gin, GORM, and System Architecture.
 Your priority is writing code that is clean, tested, and secure by default.