Remove repo-local /loki-query command; superseded by global skill

The /loki-query slash command and tools/loki/ scripts are replaced by a global
'loki-query' Claude skill (hosted in the Mantis repo, symlinked into
~/.claude/skills/), now generalized to query Loki for any app on the cluster
(VCell, sms-api, compose-api, ...). All VCell-specific guidance (container tables,
broker/supervisord archaeology, JMS-wedge workflow) is preserved in the skill's
VCell section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QtHfpXHt1sXcDUUsXWYEpM

Author: jcschaff