fix: Remove Matrix integration — notifications move to forge + OpenClaw (#732)

Remove all Matrix/Dendrite infrastructure:
- Delete lib/matrix_listener.sh (long-poll daemon), lib/matrix_listener.service
  (systemd unit), lib/hooks/on-stop-matrix.sh (response streaming hook)
- Remove matrix_send() and matrix_send_ctx() from lib/env.sh
- Remove MATRIX_HOMESERVER auto-detection, MATRIX_THREAD_MAP from lib/env.sh
- Remove [matrix] section parsing from lib/load-project.sh
- Remove Matrix hook installation from lib/agent-session.sh
- Remove notify/notify_ctx helpers and Matrix thread tracking from
  dev/dev-agent.sh and action/action-agent.sh
- Remove all matrix_send calls from dev-poll.sh, phase-handler.sh,
  action-poll.sh, vault-poll.sh, vault-fire.sh, vault-reject.sh,
  review-poll.sh, review-pr.sh, supervisor-poll.sh, formula-session.sh
- Remove Matrix listener startup from docker/agents/entrypoint.sh
- Remove append_dendrite_compose() and setup_matrix() from bin/disinto
- Remove --matrix flag from disinto init
- Clean Matrix references from .env.example, projects/*.toml.example,
  formulas/*.toml, AGENTS.md, BOOTSTRAP.md, README.md, RESOURCES.md,
  PHASE-PROTOCOL.md, and all agent AGENTS.md/PROMPT.md files

Status visibility now via Codeberg PR/issue activity. Human interaction
via vault items through forge. Proactive alerts via OpenClaw heartbeats.

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

docker/agents/entrypoint.sh

@@ -87,14 +87,6 @@ else
   log "tea login: skipped (tea not found or FORGE_TOKEN/FORGE_URL not set)"
 fi
 
-# Start matrix listener in background (if configured)
-if [ -n "${MATRIX_TOKEN:-}" ] && [ -n "${MATRIX_ROOM_ID:-}" ]; then
-  log "Starting matrix listener in background"
-  su -s /bin/bash agent -c "${DISINTO_DIR}/lib/matrix_listener.sh" &
-else
-  log "Matrix listener: skipped (MATRIX_TOKEN or MATRIX_ROOM_ID not set)"
-fi
-
 # Run cron in the foreground.  Cron jobs execute as the agent user.
 log "Starting cron daemon"
 exec cron -f