fix: use get_hermes_home() for profile-scoped storage, fix README

- Replace hardcoded os.path.expanduser('~/.hermes') with
  get_hermes_home() from hermes_constants for profile isolation
- Fix README echo command quoting error

plugins/memory/supermemory/README.md

@@ -17,7 +17,7 @@ Or manually:
 
 ```bash
 hermes config set memory.provider supermemory
-echo 'SUPERMEMORY_API_KEY=***' >> ~/.hermes/.env
+echo 'SUPERMEMORY_API_KEY=your-key-here' >> ~/.hermes/.env
 ```
 
 ## Config