docs: document pm3py client in the README

Adds a feature bullet, a `pm3py client` section (usage, the SWIG/pexpect backends, completion + press-right help + coloured output) and a 'Distributing a drop-in' subsection for --pack; notes the pexpect dependency and the clientcli package in the tree. rawcli content untouched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -8,6 +8,7 @@ Pure-Python async client for the [Proxmark3](https://github.com/RfidResearchGrou
 - **Live sniff & simulation** — stream decoded reader↔tag frames into your REPL in real time; edit an emulated tag and push it live.
 - **Software-defined tags** — pure-Python transponder models (ISO 14443-A, ISO 15693, MIFARE Classic, NTAG/Type-2, NXP ICODE/SLIX2/NTAG5, LF) served from a firmware response table.
 - **Interactive raw console** — [`pm3py rawcli`](#pm3py-rawcli--interactive-raw-command-console) drops into a Proxmark-style TUI for raw command entry: a live annotated trace, hex/binary toggle, and function-style transponder commands.
+- **Autocompleting client** — [`pm3py client`](#pm3py-client--autocompleting-console-for-the-stock-proxmark3-client) wraps the **stock Proxmark3 client** (so it works with any Proxmark/firmware) with full command-tree completion, press-→ help, and the client's own colored output — and can [spin off a single-file drop-in](#distributing-a-drop-in) for anyone on the stock repo.
 
 ## Install
 
@@ -21,7 +22,7 @@ pip install -e .            # or `pip install .`
 ```
 
 Requires **Python 3.10+**; dependencies (`pyserial-asyncio`, `bitarray`, `pycryptodome`,
-`prompt_toolkit`) install automatically. It's pure Python + pyserial, so it also runs on a **Raspberry Pi**
+`prompt_toolkit`, `pexpect`) install automatically. It's pure Python + pyserial, so it also runs on a **Raspberry Pi**
 (aarch64) — see [Flashing firmware](#flashing-firmware-pm3flash) for the Pi bring-up.
 
 ## Quick Start
@@ -527,6 +528,57 @@ NTAG213  (HF / 14a)  UID 04A1B2C3
 - **ipython-style completion** — command/argument menus with each command's help as the tooltip,
   plus history auto-suggestion.
 
+## `pm3py client` — autocompleting console for the stock Proxmark3 client
+
+Where `rawcli` speaks pm3py's own protocol stack, `pm3py client` wraps the **standard Proxmark3 C
+client** — so it works with any Proxmark3 and any firmware the stock client supports. You get the
+real client's exact behavior and its native colored output, with autocompletion and inline help
+layered over its full command tree.
+
+```bash
+pm3py client                     # auto-detect the device and the client
+pm3py client --driver pexpect    # force the binary backend (no SWIG build needed)
+pm3py client --port /dev/ttyACM0 --commands /path/to/commands.json
+```
+
+```text
+[client / usb] pm3py --> hf mf rd⇥        # Tab completes to `hf mf rdbl`, then descends to its options
+[client / usb] pm3py --> hf mf rdbl --blk 0 -k FFFFFFFFFFFF
+ [+]   0 | 04 A1 B2 C3 D4 08 04 00 62 63 64 65 66 67 68 69 |   # the client's own colored output
+[client / usb] pm3py --> hf 14a in⇥       # → on the highlighted `info` opens its full help in the bar
+```
+
+- **Full command-tree completion** — completes each level (`hf` → `hf mf` → `hf mf rdbl`) and a
+  command's option flags (`--blk`, `-k`), each with its description as the tooltip. **Tab** commits
+  the highlighted item and descends to the next level.
+- **Press-→ help** — with a completion highlighted, **→** expands its full help (description, usage,
+  options, notes) in the bottom bar; **←** / **Esc** / **Ctrl-g** backs out. Otherwise the bar shows
+  a one-line hint for the current command.
+- **The client's own output** — commands run through the real client and print its native colored
+  output verbatim; the breadcrumb `[client / usb]` reflects the live connection.
+- **Two backends** (`--driver auto`, the default):
+  - **SWIG** — the in-process `_pm3` bindings (`console()` + captured output); needs the client's
+    `experimental_lib` extension built, and a connected device.
+  - **pexpect** — spawns the `proxmark3` binary and reads its prompts; no build required, and runs
+    offline. Used automatically when `_pm3` isn't importable, or forced with `--driver pexpect`.
+- **Command tree from the client** — the menu is built from the checkout's `doc/commands.json` (the
+  same set the client itself exposes), auto-located from the repo; override with `--commands`.
+
+### Distributing a drop-in
+
+`pm3py client --pack` spins off a **self-contained** copy for people who use the stock Iceman/RRG
+Proxmark3 repo but not pm3py:
+
+```bash
+pm3py client --pack pm3cli.py     # one readable file — needs `pip install prompt_toolkit pexpect`
+pm3py client --pack pm3cli.pyz    # a zipapp with those deps bundled — runs on bare `python3`
+```
+
+Drop the file into (or beside) a Proxmark3 checkout and run it (`python3 pm3cli.py`). It finds the
+checkout's `doc/commands.json` and client automatically — walking up from where it's dropped, or via
+`$PM3_REPO` — auto-detects `/dev/ttyACM*`, and gives the same console. The file is generated from
+`pm3py/cli/clientcli/` (the tested source of truth), so it never drifts.
+
 ## Firmware Compatibility
 
 On connect, pm3py pings the device and fetches the firmware version. The result is on
@@ -619,7 +671,7 @@ pm3py/
 │   ├── decode_iso14a.py / decode_iso15.py   # per-protocol decoders
 │   ├── ndef.py          # NDEF TLV/record decode
 │   └── format.py        # ANSI color trace formatting
-├── cli/            # `pm3py` console-script: rawcli (interactive raw-command TUI)
+├── cli/            # `pm3py` console-script: rawcli (raw-command TUI) + clientcli (`pm3py client`)
 ├── sniff/           # SniffSession — protocol detection, live streaming lifecycle
 ├── sim/             # card-sim infrastructure: SimSession, response-table compiler,
 │                    #   Medium/Reader models, MCU bridge, replay/relay/fuzzer