the addon arc: the AddOns folder opens

- benilla loads real 1.12 addons from Interface/AddOns — TOC, XML and Lua through one loader, with per-addon saved variables, Bindings.xml and the lifecycle events addons expect
- both AddOns screens are in: the character-select list with per-addon enable state, and the ESC menu's in-game list
- the API surface is measured, not guessed — a corpus harness runs hundreds of real 1.12 addons and ranks exactly which globals, templates and verbs they demand
- the Lua dialect is the client's own, read off the binary — 5.0 semantics with the 1.12 additions, and UI source files are bytes, not UTF-8

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/benilla-ui/src/script/object/layout_methods.rs

@@ -255,7 +255,7 @@ pub(super) fn install(lua: &Lua, m: &Table) -> mlua::Result<()> {
 }
 
 /// The frame's effective scale, ε-guarded (a zero would poison the local-unit division).
-fn eff_scale(model: &Model, h: FrameHandle) -> f32 {
+pub(super) fn eff_scale(model: &Model, h: FrameHandle) -> f32 {
     let s = model
         .arena
         .frame(h)