[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/commands/workflows/plan.md

@@ -376,13 +376,15 @@ After writing the plan file, use the **AskUserQuestion tool** to present these o
 **Question:** "Plan ready at `plans/<issue_title>.md`. What would you like to do next?"
 
 **Options:**
-1. **Run `/plan_review`** - Get feedback from reviewers (DHH, Kieran, Simplicity)
-2. **Start `/work`** - Begin implementing this plan locally
-3. **Start `/work` on remote** - Begin implementing in Claude Code on the web (use `&` to run in background)
-4. **Create Issue** - Create issue in project tracker (GitHub/Linear)
-5. **Simplify** - Reduce detail level
+1. **Open plan in editor** - Open the plan file for review
+2. **Run `/plan_review`** - Get feedback from reviewers (DHH, Kieran, Simplicity)
+3. **Start `/work`** - Begin implementing this plan locally
+4. **Start `/work` on remote** - Begin implementing in Claude Code on the web (use `&` to run in background)
+5. **Create Issue** - Create issue in project tracker (GitHub/Linear)
+6. **Simplify** - Reduce detail level
 
 Based on selection:
+- **Open plan in editor** → Run `open plans/<issue_title>.md` to open the file in the user's default editor
 - **`/plan_review`** → Call the /plan_review command with the plan file path
 - **`/work`** → Call the /work command with the plan file path
 - **`/work` on remote** → Run `/work plans/<issue_title>.md &` to start work in background for Claude Code web