refactor: split the opencv-plot viewer into its own dataflow

dataflow.yml is now the camera alone, so running it no longer pulls
dora-hub over pip or needs a display. dataflow_plot.yml adds the viewer
on image_bgr for when the stream should be looked at.

dora 1.0 resolves an input's source only within the same descriptor, so
the camera node is declared in both files rather than shared, and the two
are run one at a time. CI validates both, which is what catches an output
rename that breaks only the viewer.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A65jaxrPXMN9EhBDMmMWb2

dataflow_plot.yml

@@ -0,0 +1,27 @@
+# The camera plus an opencv-plot viewer on image_bgr.
+#
+# Separate from dataflow.yml because the viewer pulls dora-hub and installs it
+# with pip, and needs a display: the camera on its own should cost neither.
+# dora has no cross-dataflow wiring, so the camera node is declared here too
+# rather than referenced — run this file or dataflow.yml, not both.
+strict_types: true
+
+nodes:
+  - id: zed-camera
+    path: bin/dora_zed
+    build: scripts/build.sh
+    inputs:
+      tick: dora/timer/millis/100
+    outputs:
+      - image_bgr
+      - depth
+      - point_cloud
+      - camera_info
+      - camera_state
+
+  - id: plot
+    git: https://github.com/dora-rs/dora-hub.git
+    build: pip install ./node-hub/opencv-plot
+    path: opencv-plot
+    inputs:
+      image: zed-camera/image_bgr