refactor: Standardize agent references to @agent-name format

- Convert direct agent name references to @agent-name format in documentation
- Preserve Task() function calls and subagent_type parameters unchanged
- Keep task content agent identifiers in original format (for display only)
- Maintain document reference paths in original format
- Update workflow architecture, task management, and execution files

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.claude/workflows/brainstorming-principles.md

@@ -26,7 +26,7 @@ Before ANY agent coordination begins, the brainstorming command MUST establish t
    - Establish agent coordination metadata
 
 ### Pre-Agent Verification
-Before delegating to conceptual-planning-agent, VERIFY:
+Before delegating to @conceptual-planning-agent, VERIFY:
 - [ ] Topic slug generated correctly
 - [ ] All required directories exist  
 - [ ] workflow-session.json initialized
@@ -103,7 +103,7 @@ Each brainstorming session maintains metadata in `session-summary.md` header:
 **Topic**: [Challenge description]  
 **Mode**: creative|analytical|strategic  
 **Perspectives**: [role1, role2, role3...]  
-**Facilitator**: conceptual-planning-agent  
+**Facilitator**: @conceptual-planning-agent  
 **Date**: YYYY-MM-DD  
 
 ## Session Overview
@@ -161,7 +161,7 @@ done
 ```
 
 ### Agent Document Assignment Protocol
-When coordinating with conceptual-planning-agent, ALWAYS specify exact output location:
+When coordinating with @conceptual-planning-agent, ALWAYS specify exact output location:
 
 **Correct Agent Delegation:**
 ```