pub async fn preamble(
browser: Option<String>,
target: Option<&str>,
trace: &mut CommandTrace,
) -> Result<Route>Expand description
Run the shared preamble: parse the <browser>[/<tab>] positional, enforce
the <tab> / --target mutual exclusion (in ONE place with ONE message),
resolve the browser, record trace.browser/trace.engine, open the
registry, and acquire the BiDi lock if applicable.
browser is the raw positional/env value; target is --target. Returns a
Route the caller dispatches on via (route.tab_name, target).