Register Appium (or another non-Selenium WebDriver-compatible server) as a Grid node using Selenium Grid 4's [relay] TOML config

Steps

1. Create a `config.toml` with a `[relay]` section pointing `url` at the running service's WebDriver endpoint, e.g. `url = "http://localhost:4723/wd/hub"`, and set `status-endpoint = "/status"`
2. Set `[node] detect-drivers = false` so Grid doesn't try to autodetect local browser drivers and instead delegates entirely to the relay
3. Declare `configs` as a flat array of `["<max-sessions>", "<json-stereotype>"]` pairs, e.g. `["5", "{\"browserName\": \"chrome\", \"platformName\": \"android\", \"appium:platformVersion\": \"11\"}"]` — the number reserves that many concurrent slots for that stereotype
4. Optionally pin `protocol-version` (e.g. `"HTTP/1.1"`) if the relayed service doesn't negotiate HTTP/2 cleanly with Grid's HttpClient
5. Start the node with `java -jar selenium-server-<version>.jar node --config config.toml` so it registers with the Hub/Router using the relay stereotypes
6. Confirm the relayed capabilities appear as normal node slots in the Grid UI/console — routing and queueing behave like any other Selenium node from that point on