fix: eliminate cross-plugin dependencies and modernize plugin.json across marketplace

Rewrites 14 commands across 11 plugins to remove all cross-plugin
subagent_type references (e.g., "unit-testing::test-automator"), which
break when plugins are installed standalone. Each command now uses only
local bundled agents or general-purpose with role context in the prompt.

All rewritten commands follow conductor-style patterns:
- CRITICAL BEHAVIORAL RULES with strong directives
- State files for session tracking and resume support
- Phase checkpoints requiring explicit user approval
- File-based context passing between steps

Also fixes 4 plugin.json files missing version/license fields and adds
plugin.json for dotnet-contribution.

Closes #433

plugins/ui-design/.claude-plugin/plugin.json

@@ -1,8 +1,10 @@
 {
   "name": "ui-design",
   "description": "Comprehensive UI/UX design plugin for mobile (iOS, Android, React Native) and web applications with design systems, accessibility, and modern patterns",
+  "version": "1.0.0",
   "author": {
     "name": "Seth Hobson",
     "email": "seth@major7apps.com"
-  }
+  },
+  "license": "MIT"
 }