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>

AGENTS.md

@@ -26,7 +26,7 @@ disinto/
 │                  supervisor-poll.sh — legacy bash orchestrator (superseded)
 ├── vault/         vault-poll.sh, vault-agent.sh, vault-fire.sh — action gating + procurement
 ├── action/        action-poll.sh, action-agent.sh — operational task execution
-├── lib/           env.sh, agent-session.sh, ci-helpers.sh, ci-debug.sh, load-project.sh, parse-deps.sh, matrix_listener.sh, guard.sh, mirrors.sh, build-graph.py
+├── lib/           env.sh, agent-session.sh, ci-helpers.sh, ci-debug.sh, load-project.sh, parse-deps.sh, guard.sh, mirrors.sh, build-graph.py
 ├── projects/      *.toml.example — templates; *.toml — local per-box config (gitignored)
 ├── formulas/      Issue templates (TOML specs for multi-step agent tasks)
 └── docs/          Protocol docs (PHASE-PROTOCOL.md, EVIDENCE-ARCHITECTURE.md)
@@ -43,7 +43,7 @@ disinto/
 - **AI**: `claude -p` (one-shot) or `claude` (interactive/tmux sessions)
 - **CI**: Woodpecker CI (queried via REST API + Postgres)
 - **VCS**: Forgejo (git + Gitea-compatible REST API)
-- **Notifications**: Matrix (optional)
+- **Notifications**: Forge activity (PR/issue comments), OpenClaw heartbeats
 
 ## Coding conventions