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.

dora-node.yml

@@ -7,33 +7,60 @@
 apiVersion: 1
 name: dora-zed
 namespace: liria
-description: ZED stereo camera source publishing a BGR image, a depth map, intrinsics and an optional point cloud
+description: ZED stereo camera source publishing an image, a depth map, intrinsics and an optional point cloud
 categories: [sensor]
 keywords: [zed, stereolabs, camera, depth, stereo, jetson]
 
 runtime: cpp
 entrypoint: bin/dora_zed
 build: scripts/build.sh
+dora: ">=1.0"
 
 inputs:
   tick:
     type: std/core/v1/UInt64
     required: true
-    description: Each tick triggers one camera grab. Connect to dora/timer/millis/N.
+    description: >-
+      Publishes the newest frame the capture thread has grabbed, or nothing if
+      none arrived since the last tick. It does not drive the camera: capture is
+      free-running at ZED_FPS, so this sets the publish rate and anything
+      captured between two ticks is dropped. Connect to dora/timer/millis/N.
 
 outputs:
-  image_bgr:
-    type: std/core/v1/UInt8
-    description: BGR image bytes, [H, W, 3]. Shape and encoding are in the metadata.
+  image:
+    type: std/media/v1/Image
+    description: >-
+      Captured frame as an Arrow struct {width, height, encoding, data}. The
+      encoding is always bgr8, three bytes per pixel.
   depth:
-    type: std/core/v1/Float32
-    description: Per-pixel depth in millimetres, [H, W]. Missing depth is 0, never inf or nan.
+    type: std/media/v1/Image
+    description: >-
+      Depth map as an Arrow struct {width, height, encoding, data}, one channel
+      per pixel -- dora has no depth type, and a depth map is an image whose
+      pixels are distances, which is how ROS spells it too. The encoding is
+      32FC1 and the `units` metadata is mm. Missing depth is 0, never inf or
+      nan.
   camera_info:
     type: std/core/v1/Float32
     description: Intrinsics [fx, fy, cx, cy], distortion in the metadata. Published once per camera session.
   point_cloud:
     type: std/core/v1/Float32
-    description: XYZRGBA point cloud. Published only when ZED_POINT_CLOUD is on.
+    description: XYZRGBA point cloud, shape in the metadata. Published only when ZED_POINT_CLOUD is on.
   camera_state:
     type: std/core/v1/String
     description: One of opening, streaming, recovering. Published on every change.
+
+example: |
+  - id: zed-camera
+    git: https://gitea.liria.cl/liria/dora-zed.git
+    tag: v0.3.0
+    build: scripts/build.sh
+    path: bin/dora_zed
+    inputs:
+      tick: dora/timer/millis/100
+    outputs:
+      - image
+      - depth
+      - point_cloud
+      - camera_info
+      - camera_state