script errors reach the player, and the bars stop lying

- an addon error shows the red script-error dialog the reference shows, and a runaway load loop can no longer freeze world entry
- food and drink show stack counts from the first login, and a paladin's aura bar lights the aura that is actually on
- logging out no longer erases the character from saved-bag addons: the player's absence is no data
- MPQ patches are discovered the way the client discovers them, and a slow arrival holds in place instead of falling through the world

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

crates/benilla-ui/src/script/stdlib.rs

@@ -128,6 +128,12 @@ pub(super) fn install(lua: &Lua) -> mlua::Result<()> {
         .set_name("=[benilla wow stdlib]")
         .set_mode(mlua::ChunkMode::Text)
         .exec()?;
+    // Remember the default handler BY IDENTITY, right after installing it — the engine-side
+    // dispatch (decision 1305) skips it (it reports into the host channel, where every dispatched
+    // message already is) and fires only a handler somebody *chose*: FrameXML's `_ERRORMESSAGE`
+    // or an addon's own.
+    let default: mlua::Function = lua.load("return geterrorhandler()").eval()?;
+    lua.set_named_registry_value(super::REG_DEFAULT_ERRORHANDLER, default)?;
     Ok(())
 }