fix: add oh-my-openagent bin alias for renamed package

After the package was renamed from oh-my-opencode to oh-my-openagent,
the bin entry only had 'oh-my-opencode'. Users running:
  npm install -g oh-my-openagent
could not invoke 'oh-my-openagent' from the command line.

Add 'oh-my-openagent' as a second bin entry pointing to the same
bin/oh-my-opencode.js entry point. Both aliases now work.

Fixes #3482

package.json

@@ -6,7 +6,8 @@
   "types": "dist/index.d.ts",
   "type": "module",
   "bin": {
-    "oh-my-opencode": "bin/oh-my-opencode.js"
+    "oh-my-opencode": "bin/oh-my-opencode.js",
+    "oh-my-openagent": "bin/oh-my-opencode.js"
   },
   "files": [
     "dist",