docs: write CLI docs for all 12 previously undocumented tools

Add docs/cli/ entries for:
  transport_cli, discovery_cli, config_cli, protocol_cli, query_cli,
  test_image_cli, xorg_cli, v4l2_view_cli, stream_send_cli,
  stream_recv_cli, reconciler_cli, controller_cli

Each doc covers: description, build instructions, full usage with all
options and defaults, example output, and a relationship note pointing
to related tools. controller_cli includes the display control IDs table
and notes its temporary status.

README.md: convert all CLI tool entries to links.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/cli/transport_cli.md

@@ -0,0 +1,69 @@
+# transport_cli
+
+A development tool for exercising the transport layer. Starts a framed-TCP server (which echoes received frames) or a client that connects and sends a sequence of test frames.
+
+---
+
+## Build
+
+From the repository root:
+
+```sh
+make cli
+```
+
+The binary is placed in `build/cli/`.
+
+---
+
+## Usage
+
+### Server mode
+
+Listen on a port and echo back every frame received:
+
+```sh
+./transport_cli server <port> [max_connections]
+```
+
+Example:
+
+```sh
+./transport_cli server 8000
+```
+
+Output (per received frame):
+
+```
+received frame: type=0x0001 len=8
+```
+
+### Client mode
+
+Connect to a server and send three test frames:
+
+```sh
+./transport_cli client <host> <port>
+```
+
+Example:
+
+```sh
+./transport_cli client 127.0.0.1 8000
+```
+
+Each frame carries a fixed payload with a counter:
+
+```
+frame 0: payload = deadbeef 00000000
+frame 1: payload = deadbeef 00000001
+frame 2: payload = deadbeef 00000002
+```
+
+---
+
+## Relationship to the Video Routing System
+
+`transport_cli` exercises the `transport` module, which provides the framed TCP stream used by all node-to-node communication. The frame header (message type + payload length) and single-write send are the building blocks for the protocol layer.
+
+See also: [`protocol_cli.md`](protocol_cli.md) for typed message-level testing.