docs: rename general-purpose agent to universal-executor and update documentation

Major updates in this release:

1. Agent Renaming (13 files, 21 references):
   - Renamed general-purpose → universal-executor to avoid naming conflicts
   - Updated all references in commands and workflows
   - Maintained backward compatibility in documentation

2. README Updates (4 files):
   - Removed /workflow:session:start step (auto-created by /workflow:plan)
   - Simplified workflow from 4 steps to 3 steps
   - Updated version to v4.6.2
   - Added CLI tool usage guidelines

3. GETTING_STARTED Enhancements (2 files):
   - Added Design Philosophy section explaining multi-model CLI integration
   - Added comprehensive CLI tool usage guide with common workflows
   - Reorganized quick start to emphasize automatic session creation
   - Added examples for bug fixes and feature development

Files modified:
- Agent config: .claude/agents/general-purpose.md
- Commands: 7 files in .claude/commands/
- Workflows: 5 files in .claude/workflows/
- Documentation: README.md, README_CN.md, GETTING_STARTED.md, GETTING_STARTED_CN.md

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

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

README.md

@@ -73,18 +73,18 @@ The best way to get started is to follow the 5-minute tutorial in the [**Getting
 
 Here is a quick example of a common development workflow:
 
-1.  **Start a Session**:
-    ```bash
-    /workflow:session:start "Implement user login feature"
-    ```
-2.  **Create a Plan**:
+1.  **Create a Plan** (automatically starts a session):
     ```bash
     /workflow:plan "Implement JWT-based user login and registration"
     ```
-3.  **Execute the Plan**:
+2.  **Execute the Plan**:
     ```bash
     /workflow:execute
     ```
+3.  **Check Status** (optional):
+    ```bash
+    /workflow:status
+    ```
 
 ---