iris: load application-owned fonts

docs/PLAN.md

@@ -813,6 +813,13 @@ widget changed. Winit's user-event proxy and Android's posted callback are
 private implementations of that wake; applications do not define platform
 event types or manually request redraws.
 
+**Iris ships no fonts.** Applications register their own font bytes on `Ui`
+before the first text shape and select them through the same `Family` used by
+text widgets. `Family::Icons` is a semantic application-configured role, not a
+particular icon set owned by the framework. ai-app owns its Nerd Fonts subset,
+its codepoints, its license and the script that rebuilds it; body and monospace
+families continue to come from the platform.
+
 `cargo-iris` is an installable Cargo subcommand, rather than a script callers
 must find inside an Iris checkout. `cargo iris apk` builds the Rust `cdylib`
 with cargo-ndk and packages it directly with the installed Android SDK tools: