feat(copilot): add VPCS Telnet driver with Netmiko and ANSI code stripping

Implement custom VPCS driver and unified tool architecture:

   - Add VPCSTelnet custom driver (vpcs_telnet.py)
     - No authentication (direct console access like VPCS behavior)
     - Simple prompt pattern matching (PC\d+>)
     - Automatic ANSI escape code stripping for clean output
     - Config mode methods return empty (VPCS has no config modes)

   - Replace vpcs_tools_telnetlib3.py with vpcs_tools_netmiko.py
     - Migrate from telnetlib3 to Netmiko + Nornir architecture
     - Unified tool architecture matching config/display tools
     - Improved code consistency and maintainability

   - Add comprehensive test coverage (test_vpcs_telnet.py)
     - 30 unit tests covering all VPCS driver functionality
     - Tests for ANSI code stripping, telnet_login, send_command
     - Tests for device registration and initialization

   - Update VPCS built-in template (services/templates.py)
     - Add platform:vpcs and device_type:gns3_vpcs_telnet tags
     - Automatic driver selection without manual configuration

   - Update documentation (docs/)
     - multi-vendor-device-support.md: VPCS driver documentation
     - netmiko_devices.md: Add VPCS to supported devices list
     - README.md: Update multi-vendor support description

gns3server/agent/gns3_copilot/tools_v2/__init__.py

@@ -30,13 +30,13 @@ This package provides various tools for interacting with GNS3 network simulator:
 - Device configuration command execution
 - Display command execution
 - Multiple device command execution using Nornir
-- VPCS device configuration using telnetlib3
+- VPCS device configuration using Netmiko
 - Node and link management
 
 Main modules:
 - config_tools_nornir: Multiple device configuration command execution tool using Nornir
 - display_tools_nornir: Multiple device command execution tool using Nornir
-- vpcs_tools_telnetlib3: VPCS device configuration tool using telnetlib3
+- vpcs_tools_netmiko: VPCS device configuration tool using Netmiko
 - gns3_create_node: GNS3 node creation tool
 - gns3_create_link: GNS3 link creation tool
 - gns3_start_node: GNS3 node startup tool
@@ -59,7 +59,6 @@ from .gns3_start_node import GNS3StartNodeTool
 from .gns3_stop_node import GNS3StopNodeTool
 from .gns3_suspend_node import GNS3SuspendNodeTool
 from .gns3_update_node_name import GNS3UpdateNodeNameTool
-from .vpcs_tools_telnetlib3 import VPCSMultiCommands
 
 # Dynamic version management
 try:
@@ -77,7 +76,6 @@ __url__ = "https://github.com/yueguobin/gns3-copilot"
 __all__ = [
     "ExecuteMultipleDeviceConfigCommands",
     "ExecuteMultipleDeviceCommands",
-    "VPCSMultiCommands",
     "GNS3CreateNodeTool",
     "GNS3LinkTool",
     "GNS3StartNodeTool",