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>

lib/agent-session.sh

@@ -290,32 +290,6 @@ create_agent_session() {
     fi
   fi
 
-  # Install Stop hook for Matrix streaming: when MATRIX_THREAD_ID is set,
-  # each Claude response is posted to the Matrix thread so humans can follow.
-  local matrix_hook_script="${FACTORY_ROOT}/lib/hooks/on-stop-matrix.sh"
-  if [ -n "${MATRIX_THREAD_ID:-}" ] && [ -x "$matrix_hook_script" ]; then
-    if [ -f "$settings" ]; then
-      jq --arg cmd "$matrix_hook_script" '
-        if (.hooks.Stop // [] | any(.[]; .hooks[]?.command == $cmd))
-        then .
-        else .hooks.Stop = (.hooks.Stop // []) + [{
-          matcher: "",
-          hooks: [{type: "command", command: $cmd}]
-        }]
-        end
-      ' "$settings" > "${settings}.tmp" && mv "${settings}.tmp" "$settings"
-    else
-      jq -n --arg cmd "$matrix_hook_script" '{
-        hooks: {
-          Stop: [{
-            matcher: "",
-            hooks: [{type: "command", command: $cmd}]
-          }]
-        }
-      }' > "$settings"
-    fi
-  fi
-
   rm -f "$idle_marker"
   local model_flag=""
   if [ -n "${CLAUDE_MODEL:-}" ]; then