add typed Arrow payloads and a dora-image-view dataflow

dora-image-view takes std/media/v1/Image, and dora's compatibility graph
has no edge from std/core/v1/UInt8 to it, so wiring the two failed
`dora validate` whatever the node actually sent. Its flat-buffer fallback
would not have decoded these frames either: it reads width/height
metadata, and this node only published shape.

image and depth now go out as the Image struct, camera_info and
point_cloud as Float32 arrays and camera_state as a string, all built
against the Arrow C data interface in src/arrow so the node still links
no Arrow C++. Shape, dtype and encoding metadata are dropped where the
payload describes itself; intrinsics, frame_id and both timestamps are
unchanged. tests/run.sh covers the packing without a camera or the SDK,
round-tripping each array through pyarrow and rebuilding it under the
sanitizers.

Breaking: image_bgr is renamed to image and every payload changes shape.
dataflow_plot.yml is replaced by dataflow_view.yml, which wires the
viewer from a tag and repeats its contract in input_types so validate
checks both sides of the wiring.

dataflow_view.yml

@@ -0,0 +1,46 @@
+# The camera into dora-image-view, and the worked example of wiring this node to
+# a consumer.
+#
+# 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.
+#
+# Run it with `--uv`, which gives the viewer its own managed environment:
+#
+#     dora run dataflow_view.yml --uv
+#
+# Fetching the viewer needs anonymous read access to its repository. dora-cli
+# 1.0.1 fetches through libgit2 with no credential callback, so ssh:// cannot
+# authenticate at all; on Gitea, marking the repository public is not enough
+# either, since a repository inside a private organization answers an anonymous
+# clone with 401.
+strict_types: true
+
+nodes:
+  - id: zed-camera
+    path: bin/dora_zed
+    build: scripts/build.sh
+    inputs:
+      tick: dora/timer/millis/100
+    outputs:
+      - image
+      - depth
+      - point_cloud
+      - camera_info
+      - camera_state
+
+  - id: view
+    git: https://gitea.liria.cl/liria/dora-image-view.git
+    tag: v0.1.0
+    build: uv pip install .
+    path: dora-image-view
+    inputs:
+      image: zed-camera/image
+      depth: zed-camera/depth
+      camera_info: zed-camera/camera_info
+    # The viewer's own manifest says this, but a `git:` node's manifest is not
+    # read at validate time — only at build. Repeating it here is what makes the
+    # two contracts checked against each other now rather than at runtime.
+    input_types:
+      image: std/media/v1/Image
+      depth: std/media/v1/Image
+      camera_info: std/core/v1/Float32