dsh-capitalize: Capitalize the First Letter

The DeepSeek Harness (DSH) plugin dsh-capitalize is a string-processing tool implemented purely in Node.js. It is designed to apply formatting adjustments to text generated by agents and does not rely on network requests. The plugin is maintained by uckkk and is released under the MIT license. Users can install it using `dsh plugin add github:uckkk/dsh-capitalize`. Once installed, it can be invoked directly in a conversation. It depends on `@deepseek-ai/cordis` (^4.0.1) and `@deepseek-ai/dsh-tools` (>=0.1.0-rc.6).