Add openlogi-hid-web: a HidBackend over WebHID

New crate implementing `HidBackend` on `web-sys`'s WebHID bindings (still behind `--cfg=web_sys_unstable_apis`). Scope: request/open a device from a user gesture, map the HID++ short/long report collections, feed reads into the de-threaded read path, surface disconnects.

Depends on the timer and read-loop issues in this epic; until both land this crate can compile but not run.

Start by reviewing the HidBackend interface and the timer and read-loop issues this crate depends on, then inspect the web-sys WebHID bindings. Implement the openlogi-hid-web crate so it requests and opens a device from a user gesture, maps HID++ short and long report collections, feeds reads into the de-threaded read path, and surfaces disconnects.

Written by the indexing model from the issue text.