add matrix orchestrator rail and repo scaffolding

rails/orchestrator-matrix/adapters/README.md

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+# Adapter Contract
+
+Runtime adapters translate task commands into concrete worker invocations.
+
+## Minimal Contract
+
+Each task should define either:
+
+1. `command` directly in `tasks.json`, or
+2. controller-level `worker.command_template` in `.mosaic/orchestrator/config.json`
+
+`command_template` may use:
+
+- `{task_id}`
+- `{task_title}`
+- `{task_file}`
+
+## Examples
+
+Codex:
+
+```json
+{
+  "worker": {
+    "command_template": "codex \"run task {task_id}: {task_title}\""
+  }
+}
+```
+
+Claude:
+
+```json
+{
+  "worker": {
+    "command_template": "claude -p \"Execute task {task_id}: {task_title}\""
+  }
+}
+```
+
+OpenCode:
+
+```json
+{
+  "worker": {
+    "command_template": "opencode \"execute task {task_id}: {task_title}\""
+  }
+}
+```
+
+## Recommendation
+
+Prefer explicit per-task `command` for deterministic execution and auditability.