add matrix orchestrator rail and repo scaffolding

rails/orchestrator-matrix/README.md

@@ -0,0 +1,50 @@
+# Mosaic Matrix Orchestrator Rail
+
+Runtime-agnostic orchestration rail for delegating work to worker agents and enforcing
+mechanical quality gates.
+
+## Purpose
+
+- Decouple orchestration from any single agent runtime feature set
+- Persist state in repo-local `.mosaic/orchestrator/` files
+- Emit structured events for Matrix transport and audit trails
+- Enforce rails before marking tasks complete
+
+## Components
+
+- `protocol/` - JSON schemas for task/event payloads
+- `controller/mosaic_orchestrator.py` - deterministic controller loop
+- `adapters/` - runtime adapter guidance
+
+## Repo Contract
+
+The controller expects this layout in each bootstrapped repo:
+
+```text
+.mosaic/orchestrator/
+  config.json
+  tasks.json
+  state.json
+  events.ndjson
+  logs/
+  results/
+```
+
+## Quick Start
+
+From a bootstrapped repo:
+
+```bash
+~/.mosaic/bin/mosaic-orchestrator-run --once
+```
+
+Continuous loop:
+
+```bash
+~/.mosaic/bin/mosaic-orchestrator-run --poll-sec 10
+```
+
+## Matrix Note
+
+This rail writes canonical events to `.mosaic/orchestrator/events.ndjson`.
+Matrix bridge services can consume and relay these events to Matrix rooms.