Add git diff instruction to review prompt

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@because/sandlot",
-  "version": "0.0.21",
+  "version": "0.0.23",
   "description": "Sandboxed, branch-based development with Claude",
   "type": "module",
   "bin": {

src/commands/review.ts

@@ -26,6 +26,8 @@ Each one should deliver you a report in this format (the <tags> are just for you
 Description of problem.
 </agentOutput>
 
+Tell each agent: Run \`git diff main...HEAD\` and focus on the "+" lines, not the "-" lines.
+
 Once the agents are done, look at all their suggestions and let me know what you think.
 `
   if (extra) prompt += "\n\n" + extra