add a dora-node.yml manifest and a dora validate CI gate

No source package is shared between node repositories, so the manifest and its
type URNs are the only contract a consumer has. Declaring them makes a wiring
mistake fail at validate time with the producer and consumer URNs, instead of
at runtime.

Every payload this node sends is a raw buffer whose shape and dtype live in the
metadata rather than an Arrow struct, so the URNs name the element type:
UInt8 for image_bgr, Float32 for depth, camera_info and point_cloud, String for
camera_state. tick is UInt64, matching how dora types timer inputs.

dataflow.yml now builds the node from the checkout with path: + build:. A
git:-sourced node does not pick up an adjacent manifest, so validating the
previous form checked nothing; with path: the CLI reports "injected 6 contract
type(s)" and a deliberately mismatched annotation exits non-zero under
strict_types. The README keeps the tag: form for consumers.

The workflow needs no camera and no ZED SDK, since validation never runs the
node. Also ignores the git/ and out/ working directories dora build creates,
and drops the ignore rules for the deleted test assets.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7g2cBJ5e3r15ZbJ9WZn8c

dataflow.yml

@@ -1,9 +1,12 @@
+# The repository's own example: builds and runs the node from this checkout, so
+# `dora validate` picks up the typed contract in dora-node.yml next to it.
+# A consumer wires the node from a tag instead — see README.md.
+strict_types: true
+
 nodes:
   - id: zed-camera
-    git: ssh://git@gitea.liria.cl:5001/liria/dora-zed.git
-    tag: v0.2.0
-    build: scripts/build.sh
     path: bin/dora_zed
+    build: scripts/build.sh
     inputs:
       tick: dora/timer/millis/100
     outputs: