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/hooks/on-stop-matrix.sh

@@ -1,45 +0,0 @@
-#!/usr/bin/env bash
-# on-stop-matrix.sh — Stop hook: post Claude response to Matrix thread.
-#
-# Called by Claude Code after each assistant turn. Reads the response from
-# the hook JSON and posts it to the Matrix thread for this action session.
-#
-# Requires env vars: MATRIX_THREAD_ID, MATRIX_TOKEN, MATRIX_HOMESERVER, MATRIX_ROOM_ID
-#
-# Usage (in .claude/settings.json):
-#   {"type": "command", "command": "/path/to/on-stop-matrix.sh"}
-
-# Exit early if Matrix thread not configured
-if [ -z "${MATRIX_THREAD_ID:-}" ] || [ -z "${MATRIX_TOKEN:-}" ] \
-   || [ -z "${MATRIX_HOMESERVER:-}" ] || [ -z "${MATRIX_ROOM_ID:-}" ]; then
-  cat > /dev/null
-  exit 0
-fi
-
-input=$(cat)
-
-# Extract response text from hook JSON
-response=$(printf '%s' "$input" | jq -r '.last_assistant_message // empty' 2>/dev/null)
-[ -z "$response" ] && exit 0
-
-# Truncate long output for readability (keep to ~4000 chars)
-MAX_LEN=4000
-if [ "${#response}" -gt "$MAX_LEN" ]; then
-  response="${response:0:$MAX_LEN}
-... [truncated]"
-fi
-
-# Post to Matrix thread
-room_encoded="${MATRIX_ROOM_ID//!/%21}"
-txn="$(date +%s%N)$$"
-
-body=$(jq -nc \
-  --arg m "$response" \
-  --arg t "$MATRIX_THREAD_ID" \
-  '{msgtype:"m.text",body:$m,"m.relates_to":{rel_type:"m.thread",event_id:$t}}')
-
-curl -s -X PUT \
-  -H "Authorization: Bearer ${MATRIX_TOKEN}" \
-  -H "Content-Type: application/json" \
-  "${MATRIX_HOMESERVER}/_matrix/client/v3/rooms/${room_encoded}/send/m.room.message/${txn}" \
-  -d "$body" > /dev/null 2>&1 || true