chore: bump to v2.28.0 and fix repo URLs

- Bump version to 2.28.0 in plugin.json and marketplace.json
  (CHANGELOG was updated but version numbers were missed)
- Fix all repo URLs from kieranklaassen/* to EveryInc/compound-engineering-plugin
- Update component counts in docs: 28 agents, 24 commands, 15 skills, 1 MCP

Co-Authored-By: Claude <noreply@anthropic.com>

plugins/compound-engineering/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "compound-engineering",
-  "version": "2.27.0",
-  "description": "AI-powered development tools. 27 agents, 23 commands, 14 skills, 1 MCP server for code review, research, design, and workflow automation.",
+  "version": "2.28.0",
+  "description": "AI-powered development tools. 28 agents, 24 commands, 15 skills, 1 MCP server for code review, research, design, and workflow automation.",
   "author": {
     "name": "Kieran Klaassen",
     "email": "kieran@every.to",