App: Store selection in BTreeSet

Since we're using `BTreeSet` for element constraint sets now, we might
as well use it for the selection set too. This removes the `rustc-hash`
dependency.

app-proto/full-interface/Cargo.toml

@@ -11,7 +11,6 @@ default = ["console_error_panic_hook"]
 itertools = "0.13.0"
 js-sys = "0.3.70"
 nalgebra = "0.33.0"
-rustc-hash = "2.0.0"
 slab = "0.4.9"
 sycamore = "0.9.0-beta.3"
 

app-proto/full-interface/src/main.rs

@@ -4,7 +4,6 @@ mod display;
 mod outline;
 
 use nalgebra::DVector;
-use rustc_hash::FxHashSet;
 use std::collections::BTreeSet;
 use sycamore::prelude::*;
 
@@ -16,14 +15,14 @@ use outline::Outline;
 #[derive(Clone)]
 struct AppState {
     assembly: Assembly,
-    selection: Signal<FxHashSet<usize>>
+    selection: Signal<BTreeSet<usize>>
 }
 
 impl AppState {
     fn new() -> AppState {
         AppState {
             assembly: Assembly::new(),
-            selection: create_signal(FxHashSet::default())
+            selection: create_signal(BTreeSet::default())
         }
     }
 }