Function report_window_opened 

pub fn report_window_opened(
    label: String,
    kind: WindowKind,
    parent_label: Option<String>,
)

Phase B.4 — sync API: report a window open to the launcher’s state mirror. Called from CEF lifecycle callbacks on the UI thread. No-op if the launcher pipe isn’t connected (task dev mode); failures to enqueue (channel closed, drain task died) are logged but don’t propagate — the host’s authoritative state is unaffected, the mirror just falls behind. B.5 tightens.