feat(zenoh): inbound ros2:// links (design 053 s10)

[lxsaah]

Stage s10 of docs/design/053-implementation-plan.md: inbound ros2:// (053 §4.3). It removes s09's temporary "inbound not supported yet" refusal.

What it does

builder.configure::<SpindleCommand>("cell4.spindle.cmd", |reg| {
    reg.buffer(BufferCfg::Mailbox).linked_from("ros2://cell4/spindle_cmd");
});

• Routes: InboundDispatch::new(db, "ros2", &ExactGrammar), with each route's facts read from routes(), the API from s04.
• One subscription token (MS) per inbound link, carrying that link's QoS. Entity ids continue after the publishers'.
• One Zenoh subscriber per distinct topic, on its rmw_zenoh data key and remote-only. Its callback dispatches each put under the link topic, so core's exact router hands the value to every record linked to that topic. Deletes are ignored, and the attachment isn't needed on the way in.
• Shared checks: link() holds what both directions verify: a valid ROS topic name, a registered type, CDR on the wire, and the QoS overrides. Outbound adds its topic-writer refusal; inbound adds the two below.

Refusals (criterion 9, inbound rows)

Mistake	Result
A {…} pattern on ros2://	ExactGrammar refuses it in InboundDispatch::new
Two links on one topic with different ROS types	build() error naming both types
Non-CDR inbound codec (linked_from_with(url, Json))	build() error
Unregistered type	build() error
Custom deserializer	builds, with a warning: the escape hatch

The custom-serializer and custom-deserializer warning is now a value that the planning step returns and build() logs once the configuration is valid. A unit test covers it for both cases, with the serializer alone and after a codec verb (whose recorded format it clears). No log capture is needed.

Tests

• tests/ros2_inbound.rs:

  • Against an in-process router: two records linked from one topic, in domain 7 under /cell4. Both MS tokens are present (entity ids 1 and 2, default QoS). A remote delete() followed by a CDR put delivers the value to both records, and the delete delivers nothing.
  • Every refusal above.
  • A custom deserializer builds.

• Unit test: codec_warning returns nothing for cdr, a warning when no format is recorded, and an error for any other format.

• Live ROS, with the new examples/ros2_listener.rs against Jazzy's and Lyrical's rmw_zenohd:

  • ros2 topic info -v /aimdb_cmd lists the subscription: node listener, namespace /aimdb, the type hash, KEEP_LAST (10);
  • all three messages from ros2 topic pub --times 3 arrive at the record.

  The first attempt looked empty only because the ROS CLI containers need about 20 s; I'd waited 16.

Checks

The full matrix runs in CI on this PR. Locally, as a quick signal only: the library tests (22 passed), ros2_inbound (3) and ros2_outbound (5), and cargo fmt --all -- --check.

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