feat(service): standalone tines service with Unix-socket IPC

New `tines` crate (added to workspace members) hosting a `Node<LogStore,
BtTransport>` and serving a tiny request/response IPC over a Unix-domain
socket for robots without ROS2. Four operations: `observe`, `belief`,
`events`, and `status`, over length-prefixed JSON frames.

The `serve` loop now serves each connection request-by-request (previously
it handled one request per connection, dropping the socket after the first
response). Integration tests drive `handle`/`serve` with a mock transport
that auto-acks observed broadcasts and echoes an empty Summary, so a
confidence event fires without a real BLE radio.

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = ["tines-core", "tines-sim", "tines-store", "tines-bt", "tines-ros2"]
+members = ["tines-core", "tines-sim", "tines-store", "tines-bt", "tines-ros2", "tines"]
 resolver = "2"
 
 [workspace.package]