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>

.env.example

@@ -38,16 +38,6 @@ WOODPECKER_DB_USER=woodpecker              # [CONFIG] Postgres user
 WOODPECKER_DB_HOST=127.0.0.1              # [CONFIG] Postgres host
 WOODPECKER_DB_NAME=woodpecker              # [CONFIG] Postgres database name
 
-# ── Matrix (optional — real-time notifications & escalation replies) ──────
-# In compose mode, Dendrite runs inside the Docker network. `disinto init`
-# provisions the bot user, room, and token automatically.
-#   Compose:    MATRIX_HOMESERVER defaults to http://dendrite:8008 (set by env.sh)
-#   Bare metal: MATRIX_HOMESERVER defaults to http://localhost:8008
-MATRIX_HOMESERVER=http://dendrite:8008     # [CONFIG] Dendrite URL (compose default)
-MATRIX_BOT_USER=@factory-bot:disinto.local # [CONFIG] bot's Matrix user ID
-MATRIX_TOKEN=                              # [SECRET] bot's access token (auto-provisioned)
-MATRIX_ROOM_ID=                            # [CONFIG] coordination room ID (auto-provisioned)
-
 # ── Project-specific secrets ──────────────────────────────────────────────
 # Store all project secrets here so formulas reference env vars, never hardcode.
 BASE_RPC_URL=                              # [SECRET] on-chain RPC endpoint