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>

.claude/commands/task/execute.md

@@ -19,7 +19,7 @@ argument-hint: "task-id"
     -   Executes step-by-step, requiring user confirmation at each checkpoint.
     -   Allows for dynamic adjustments and manual review during the process.
 -   **review**
-    -   Optional manual review using `@general-purpose`.
+    -   Optional manual review using `@universal-executor`.
     -   Used only when explicitly requested by user.
 
 ### 🤖 **Agent Selection Logic**
@@ -45,7 +45,7 @@ FUNCTION select_agent(task, agent_override):
             WHEN CONTAINS "Execute tests", "Fix tests", "Validate":
                 RETURN "@test-fix-agent" // type: test-fix
             WHEN CONTAINS "Review code":
-                RETURN "@general-purpose" // Optional manual review
+                RETURN "@universal-executor" // Optional manual review
             DEFAULT:
                 RETURN "@code-developer" // Default agent
         END CASE
@@ -236,7 +236,7 @@ Different agents receive context tailored to their function, including implement
 - Error conditions to validate from implementation.context_notes.error_handling
 - Performance requirements from implementation.context_notes.performance_considerations
 
-**`@general-purpose`**:
+**`@universal-executor`**:
 - Used for optional manual reviews when explicitly requested
 - Code quality standards and implementation patterns
 - Security considerations from implementation.context_notes.risks