Old "Lua" output channel remains active after restarting server

還沒有人認領這個 Issue。

### Which OS are you using?

MacOS

### Expected Behaviour

When restarting the language server, I expect the output channel to be either
- cleared and reused by the new server instance
- or deleted and a new one used to replace it

### Actual Behaviour

The old channel is never destroyed, leaving multiple channels with the same name which can be confusing if you're looking for new channel output.

### Reproduction steps

1. Open a Lua file
2. Run the `Lua: Restart Language Server` command (many times makes it more obvious)
3. Open the output channel selector dropdown (`Output: Show Output Channels...`)

### Additional Notes

I think this is probably pretty simple to fix, just by either `clear()`ing and reusing or `destroy()`ing the [OutputChannel](https://code.visualstudio.com/api/references/vscode-api#OutputChannel) used for logging.

### Log

[file_Users_ianchamberlain_Documents_Development_moon-rs-ls.log](https://github.com/user-attachments/files/19100943/file_Users_ianchamberlain_Documents_Development_moon-rs-ls.log)

從 `Lua: Restart Language Server` 命令的 handler 開始，追蹤其 VS Code `OutputChannel` 的建立和保留方式。反覆執行重新啟動，然後確認 `Output: Show Output Channels...` 中只包含目前的 Lua channel，且新的 server 輸出會出現在其中。

由索引模型根據 Issue 內容生成。