docs: add no-docker-first run modes and quick start

docs/RUN_MODES.md

@@ -0,0 +1,35 @@
+# Run Modes
+
+WhisperGate has two runtime components:
+
+1. `plugin/` (OpenClaw plugin)
+2. `no-reply-api/` (deterministic NO_REPLY service)
+
+Docker is optional.
+
+## Mode A (recommended): No Docker
+
+```bash
+cd no-reply-api
+node server.mjs
+```
+
+Then configure OpenClaw provider `baseURL` to `http://127.0.0.1:8787/v1`.
+
+## Mode B: Docker
+
+```bash
+./scripts/dev-up.sh
+# or: docker compose up -d --build whispergate-no-reply-api
+```
+
+Stop:
+
+```bash
+./scripts/dev-down.sh
+```
+
+## Security notes
+
+- Bind API to loopback/private network.
+- If exposed beyond localhost, set `AUTH_TOKEN`.