[2.9.3] Add "Open plan in editor" option to /plan command

- Added "Open plan in editor" as the first option in post-generation menu
- Opens plan file in user's default editor for review before next steps
- Reordered options: open → review → work → work remote → create issue → simplify

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

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

@@ -1,6 +1,6 @@
 {
   "name": "compound-engineering",
-  "version": "2.9.2",
+  "version": "2.9.3",
   "description": "AI-powered development tools. 24 agents, 19 commands, 11 skills, 2 MCP servers for code review, research, design, and workflow automation.",
   "author": {
     "name": "Kieran Klaassen",