add cli for server-side

docs/cli.md

@@ -0,0 +1,70 @@
+# nexus-cli
+
+`nexus-cli` is a small non-interactive CLI for the nexus-sync server API.
+
+## Install for development
+
+```bash
+pip install -e .
+nexus-cli --help
+```
+
+The default server URL is `http://127.0.0.1:5852`. Override it with
+`--server-url` or `-s`.
+
+## List clients
+
+```bash
+nexus-cli --list
+```
+
+## Show client info
+
+```bash
+nexus-cli client linux-client
+```
+
+The output includes basic client metadata and advertised `available_commands`.
+
+## Queue a command for a client
+
+```bash
+nexus-cli client linux-client --run-command hostname
+nexus-cli client linux-client --run-command hostname --timeout-seconds 30
+```
+
+Payload shape:
+
+```json
+{
+  "name": "hostname",
+  "args": {},
+  "timeout_seconds": 30
+}
+```
+
+## Show command execution info
+
+```bash
+nexus-cli command cmd_123
+```
+
+If the client has reported a result, stdout and stderr are printed.
+
+## JSON output
+
+Use `--json` for machine-readable output:
+
+```bash
+nexus-cli --json --list
+nexus-cli --json client linux-client
+nexus-cli --json command cmd_123
+```
+
+## Build standalone binary
+
+```bash
+make cli
+```
+
+This creates `dist/nexus-cli` through PyInstaller.