dsh-plugin-forge-preset: Codify the "write, read, and modify plugins" workflow into a preset.

Once installed, the DSH agent preset by maintainer wodaimnd adds "Plugin Workshop" to the mode dropdown, covering three types of tasks: writing plugins from scratch, understanding existing plugins, and absorbing and modifying forks. It comprises four internal roles: plugin mapping, code absorption, modification forking, and regression verification, supported by 7 skills and four retrieval tools: outline generator, index database, ast-grep, and host grep. Test data provided in the README indicates that reading 6 plugin files in full consumes 95,064 tokens, whereas reading only the structure outline consumes 1,470 tokens. The prompts are embedded in `persona.md`, `SKILL.md`, and `references/`, along with a 70KB original specification document. Installation relies on symbolic links and junctions within the profile. After restarting, the phase in `preset-declare.json` needs to be verified. Plugins run with the privileges of the current DSH process; the source code and license should be verified before installation.