refactor: dual-instance setup, remove dead container code

- Make STORE_DIR, DATA_DIR, GROUPS_DIR configurable via env vars
  (NANOCLAW_STORE_DIR, NANOCLAW_DATA_DIR, NANOCLAW_GROUPS_DIR)
  for running two instances from one codebase
- Remove broken 'both' agent type sequential loop from processGroupMessages
- Delete dead code: container-runtime, mount-security, credential-proxy,
  Dockerfiles, and related config constants (~1,085 lines removed)
- Add codex instance launchd plist template

.gitignore

@@ -6,10 +6,13 @@ dist/
 
 # Local data & auth
 store/
+store-*/
 data/
+data-*/
 logs/
 
 # Groups - only track base structure and specific CLAUDE.md files
+groups-*/
 groups/*
 !groups/main/
 !groups/global/