fix: bundled dust cleanup — lib/matrix_listener.sh (#264)

- Remove dead ROOM_ENCODED and EVENT_ID variables from matrix_listener.sh
  (were suppressed with SC2034 instead of removed)
- Remove dead REPO variable from dev-poll.sh and review-poll.sh
- Update header comment in matrix_listener.sh to list all 5 reply-routing
  cases (supervisor, gardener, dev, review, vault, action)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dev/dev-poll.sh

@@ -201,9 +201,6 @@ try_direct_merge() {
   return 1
 }
 
-# shellcheck disable=SC2034
-REPO="${CODEBERG_REPO}"
-
 API="${CODEBERG_API}"
 LOCKFILE="/tmp/dev-agent-${PROJECT_NAME:-harb}.lock"
 LOGFILE="${FACTORY_ROOT}/dev/dev-agent-${PROJECT_NAME:-harb}.log"