dsh-vditor: Replacing the DSH Web Input Card with Vditor 3.11.3

DSH plugin `dsh-vditor` rebuilds the web chat input box based on Vditor 3.11.3 (IR mode), providing a Markdown WYSIWYG experience. It supports code highlighting, KaTeX formulas, dark themes, and dynamic placeholders. For file interaction, it supports path pills, image pasting, and `@` search references. The plugin also integrates toolbar features such as slash commands, model switching, permission control, and context usage monitoring. It requires DSH ≥ 0.1.2-rc.1 and depends on an internet connection to load Vditor.