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/v4l2_view_cli.md

@@ -0,0 +1,69 @@
+# v4l2_view_cli
+
+A live camera viewer. Opens a V4L2 capture device, selects the best available format, and displays the video stream in an X11 window with a real-time FPS and format overlay. Bypasses the node system entirely — useful for verifying a camera works before wiring it into a node.
+
+---
+
+## Build
+
+From the repository root:
+
+```sh
+make cli
+```
+
+The binary is placed in `build/cli/`.
+
+Requires GLFW, OpenGL, libjpeg-turbo, and a V4L2-capable kernel.
+
+---
+
+## Usage
+
+```sh
+./v4l2_view_cli [--device PATH]
+                [--width N --height N]
+                [--format mjpeg|yuyv]
+                [--scale stretch|fit|fill|1:1]
+                [--anchor center|topleft]
+                [--x N] [--y N]
+```
+
+| Option | Default | Description |
+|---|---|---|
+| `--device PATH` | `/dev/video0` | V4L2 device to open |
+| `--width N` | auto | Capture width; if omitted, selects highest-FPS mode |
+| `--height N` | auto | Capture height |
+| `--format` | auto | Prefer `mjpeg` or `yuyv`; auto selects best available |
+| `--scale` | `fit` | Frame scaling in window |
+| `--anchor` | `center` | Frame alignment in window |
+| `--x N` | `0` | Window X position |
+| `--y N` | `0` | Window Y position |
+
+Press **Q** or **Escape** to close the window.
+
+### Auto format selection
+
+Without `--width`/`--height`, the tool selects the format with the highest frame rate, and within that the largest resolution. This is the same logic the node's ingest module uses.
+
+### Overlay
+
+Every 0.5 seconds the overlay updates with:
+
+```
+MJPEG 1280x720 @ 30.0 fps
+```
+
+### Example
+
+```sh
+./v4l2_view_cli --device /dev/video0 --scale fit
+```
+
+---
+
+## Relationship to the Video Routing System
+
+`v4l2_view_cli` is a standalone sanity-check tool. It exercises the same V4L2 format enumeration, mmap capture, MJPEG decode, and xorg rendering path that the node's ingest + display pipeline uses — but without any transport or protocol overhead.
+
+See also: [`stream_send_cli.md`](stream_send_cli.md) to capture and send over the network; [`xorg_cli.md`](xorg_cli.md) for static test patterns.