dsh-complex: DeepSeek Harness Complex Number Math Toolkit

`dsh-complex` is a complex-number computation plugin for DeepSeek Harness (DSH), aimed at addressing the low accuracy of complex-number arithmetic in large models. It uses a zero-dependency, deterministic computation design and provides six core tools: parsing, arithmetic, coordinate conversion, function evaluation, square roots, and quadratic equation solving. It supports IEEE double-precision floating-point computation, follows CPython library conventions, and handles invalid inputs by returning `valid: false`. It can be installed via the `dsh plugin` command for use in scenarios such as signal processing and control theory.