dsh-ac-size: AC Tonnage Selection

The `dsh-ac-size` plugin introduced in the DeepSeek Harness (DSH) ecosystem aims to solve the challenge of estimating air-conditioner tonnage for agents. Maintained by istone, it is a pure Node-based tool focused on local calculations based on industry experience. It has no network dependencies and can accurately return tonnage estimates based on input room parameters. The plugin is easy to install and is suitable for agents that need to handle environmental control in automated scenarios.