chore: add repository metadata

Link package metadata to GitHub mirror.

package.json

@@ -4,6 +4,10 @@
   "description": "OpenCode plugin that prevents agents/tools from reading or editing sensitive .env* files, while still allowing safe inspection via EnvSitter.",
   "license": "MIT",
   "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/boxpositron/envsitter-guard.git"
+  },
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",