event-driven UI feeds, and the character window's cost lets go

- the eight heaviest UI feeds — spellbook, party, character, bags, talents, units, pet, player — rebuild only when an input moved instead of every frame: 216 → 12 µs a frame parked
- the character window's cost settles once it closes: enchant countdowns feed by the second instead of firing an inventory event into all 20 slots every frame, the paper-doll booth parks with its camera, and a window hidden under the cursor fires OnLeave so its tooltip goes with it — the reference's hover-hide law
- the walk stops paying for finished work: the loading-screen tally's per-placement walk latches off once the world is ready, the settled placement spawner is one integer compare, and billboards stop dirtying every card's transform
- never-rendering hierarchy nodes — rig anchors, joints, doodad hosts — keep the hide chain but leave the per-camera visibility sweep: 25,198 → 18,026 swept entities at Goldshire

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

crates/benilla-app/src/ui_script/session.rs

@@ -66,12 +66,26 @@ impl<T: Default> VmMemo<T> {
     /// way into it and once on the way out, and holds in between. Reaching for a scratch default
     /// each frame instead would quietly turn the memo off for the whole glue phase.
     pub(crate) fn get_for(&mut self, script: Option<&UiScript>) -> &mut T {
+        self.get_reset_for(script).0
+    }
+
+    /// [`VmMemo::get`], also reporting whether the memory RESET on this read — i.e. this is the
+    /// first read against a new VM. A gated feed (decision 1439) keys its "must run" on exactly
+    /// this: with every input unchanged, a fresh VM still needs the full re-push, and the reset is
+    /// the only signal that says so. The flag is true at most once per session per memo, so a gate
+    /// that ORs it in costs nothing on the steady frames it exists to skip.
+    pub(crate) fn get_reset(&mut self, script: &UiScript) -> (&mut T, bool) {
+        self.get_reset_for(Some(script))
+    }
+
+    fn get_reset_for(&mut self, script: Option<&UiScript>) -> (&mut T, bool) {
         let now = script.map_or(0, UiScript::session);
-        if self.session != now {
+        let reset = self.session != now;
+        if reset {
             self.session = now;
             self.inner = T::default();
         }
-        &mut self.inner
+        (&mut self.inner, reset)
     }
 }
 
@@ -118,6 +132,25 @@ mod tests {
         );
     }
 
+    /// The gate half (1439): `get_reset` reports the reset exactly once per session flip — the
+    /// one frame a gated feed must run with every other input unchanged.
+    #[test]
+    fn get_reset_reports_each_session_flip_once() {
+        let first = UiScript::new().expect("VM");
+        let second = UiScript::new().expect("VM");
+        let mut memo: VmMemo<u32> = VmMemo::default();
+
+        let (m, reset) = memo.get_reset(&first);
+        assert!(reset, "the first read of a session is the reset");
+        *m = 7;
+        let (m, reset) = memo.get_reset(&first);
+        assert!(!reset, "steady frames read quietly");
+        assert_eq!(*m, 7);
+        let (m, reset) = memo.get_reset(&second);
+        assert!(reset, "a new VM resets again");
+        assert_eq!(*m, 0, "…and the memory is gone with the old one");
+    }
+
     #[test]
     fn a_seed_is_claimed_once_per_vm() {
         let first = UiScript::new().expect("VM");