rename node to dora-image-view

The repository, the Python package, the entrypoint and the manifest name all
now agree. `plot` was carried over from the upstream opencv-plot node and no
longer described anything here, so the module, the class and the environment
variables follow the node:

  dora_plot/         -> dora_image_view/
  dora_plot/plot.py  -> dora_image_view/view.py
  Plot               -> View
  PLOT_WIDTH/HEIGHT  -> VIEW_WIDTH/HEIGHT
  --plot-width/-height -> --view-width/-height

Breaking for anyone wiring `path: dora-plot` or setting PLOT_WIDTH; nothing is
tagged yet.

README.md

@@ -1,4 +1,4 @@
-# dora-plot
+# dora-image-view
 
 Dora node that overlays bounding boxes, labels and text on an image input and displays
 it in an OpenCV window. A display sink for debugging a vision pipeline: it produces no
@@ -13,11 +13,11 @@ Add to your dataflow:
 
 ```yaml
 nodes:
-  - id: plot
-    git: ssh://git@gitea.liria.cl:5001/liria/dora-plot.git
+  - id: view
+    git: ssh://git@gitea.liria.cl:5001/liria/dora-image-view.git
     tag: v0.1.0
     build: pip install .
-    path: dora-plot
+    path: dora-image-view
     inputs:
       image: camera/image
       bbox: detector/bbox
@@ -61,11 +61,14 @@ CI=true SOURCE_FRAMES=30 dora run dataflow.yml --uv
 
 [`dora-node.yml`](dora-node.yml) declares the node's inputs with type URNs. No source
 package is shared between node repositories, so it is the only contract a consumer has,
-and it is what makes a wiring mistake fail at build time instead of at runtime:
+and it is what makes a wiring mistake fail at build time instead of at runtime. The
+example source has a manifest of its own, so `dora validate` checks the two against
+each other:
 
 ```
 $ dora validate dataflow.yml
-  node "plot": injected 2 contract type(s) from .../dora-node.yml
+  node "source": injected 2 contract type(s) from .../examples/dora-node.yml
+  node "view": injected 2 contract type(s) from .../dora-node.yml
 All type annotations OK.
 ```
 
@@ -81,8 +84,8 @@ of that state:
 
 - An **`image`** event decodes the frame and immediately redraws: it draws every stored
   bbox (green rectangle plus `label, conf` text), draws the stored text at the top left,
-  resizes to `PLOT_WIDTH`x`PLOT_HEIGHT` if both are set, and shows it in a window titled
-  `Dora Node: dora-plot`. Press `q` in the window to quit.
+  resizes to `VIEW_WIDTH`x`VIEW_HEIGHT` if both are set, and shows it in a window titled
+  `Dora Node: dora-image-view`. Press `q` in the window to quit.
 - A **`bbox`** or **`text`** event only updates stored state; it is drawn on the next
   `image` redraw.
 
@@ -124,11 +127,11 @@ None — it is a display sink.
 
 | Variable | Default | Meaning |
 |---|---|---|
-| `PLOT_WIDTH` | image width | Resize the displayed frame to this width, in pixels. |
-| `PLOT_HEIGHT` | image height | Resize the displayed frame to this height, in pixels. |
+| `VIEW_WIDTH` | image width | Resize the displayed frame to this width, in pixels. |
+| `VIEW_HEIGHT` | image height | Resize the displayed frame to this height, in pixels. |
 
-Resizing only happens when both are set. Both are also available as `--plot-width` and
-`--plot-height`; the environment variable wins when both are given.
+Resizing only happens when both are set. Both are also available as `--view-width` and
+`--view-height`; the environment variable wins when both are given.
 
 `CI=true` suppresses the display window; it is not a configuration knob.
 
@@ -143,7 +146,9 @@ so the node installs with no system packages and no compiler on any of them —
 AVIF support, which comes from `pillow-avif-plugin` rather than OpenCV.
 
 **Requirements:** dora 1.0+ (verified with `dora-cli 1.0.1`), Python 3.11+, `uv`, and a
-display to show the window on (or `CI=true` to run without one).
+display to show the window on (or `CI=true` to run without one). On a bare Linux image
+`opencv-python` also needs the libGL shared libraries (`libgl1`, `libglib2.0-0`), which
+it links at import time.
 
 ## Test