enhance proton client page (#623)

Author: chenziliang

docs/proton-client.md

@@ -1,9 +1,40 @@
 # proton-client
 
-Timeplus Proton provides a native command-line client: `proton-client` to run SQL commands. You can also launch the client via `proton client`.
+`proton client` is the native CLI for [Timeplus Proton](/proton), shipped in
+the single `proton` binary. The alias `proton-client` forwards to
+`proton client`.
 
-For detailed usage of the SQL client, please check [timeplusd-client](/timeplusd-client), since the SQL clients in Timeplus Proton and Timeplus Enterprise share the same flags and configurations.
+The CLI shares its flags, configuration, and I/O formats with
+[`timeplusd-client`](/timeplusd-client) — see that page for usage, parameterized
+queries, and loading/dumping data. Substitute `proton client` for
+`timeplusd client` in any example.
 
 :::tip
-However, please use `proton-client` to connect to Timeplus Proton and use `timeplusd-client` to connect to the `timeplusd` in Timeplus Enterprise. Otherwise certain features won't be available and may not work. For example, when you run `proton-client` to connect to a Timeplus Enterprise deployment and try to create a [mutable stream](/mutable-stream), the `proton-client` won't accept the `CREATE MUTABLE STREAM` SQL at the client side.
+Connect to Timeplus Proton with `proton-client` and to `timeplusd` in Timeplus
+Enterprise with `timeplusd-client`. Mixing them works for basic queries but
+hides Enterprise-only features — for example, `proton-client` rejects
+`CREATE MUTABLE STREAM` on a [mutable stream](/mutable-stream) at the client
+side before the request reaches the server.
 :::
+
+## Proton-specific defaults
+
+- **History file:** `~/.proton-client-history`
+- **Config files** (first match wins): `--config-file` path → `./proton-client.xml` → `~/.proton-client/config.xml` → `/etc/proton-client/config.xml`
+- **Native TCP port:** `8463` (see [Server Ports](/proton-ports))
+
+## Quick start
+
+```bash
+# interactive shell
+proton client -h 127.0.0.1 --ask-password
+
+# one-shot query
+proton client -q "SELECT version()"
+
+# load NDJSON
+proton client -q "INSERT INTO events FORMAT JSONEachRow" < events.ndjson
+
+# dump to CSV (wrap the stream with table(...) so the query is bounded)
+proton client -q "SELECT * FROM table(events) FORMAT CSVWithNames" > events.csv
+```