Fix #2612: adjust readable trait to allow try_peek (#2714)

* Fix #2612: adjust readable trait to allow try_peek

Our implementation for Readable was inconsistent.
We had a try_unchecked variant for read but not for peek.
This resolves that by making a breaking change to the
Readable interface.

* fix doctests too

packages/signals/src/read_only_signal.rs

@@ -4,7 +4,7 @@ use std::ops::Deref;
 
 use crate::{default_impl, read_impls};
 use dioxus_core::{prelude::IntoAttributeValue, ScopeId};
-use generational_box::{Storage, UnsyncStorage};
+use generational_box::{BorrowResult, Storage, UnsyncStorage};
 
 /// A signal that can only be read from.
 pub struct ReadOnlySignal<T: 'static, S: Storage<SignalData<T>> = UnsyncStorage> {
@@ -79,8 +79,8 @@ impl<T, S: Storage<SignalData<T>>> Readable for ReadOnlySignal<T, S> {
     ///
     /// If the signal has been dropped, this will panic.
     #[track_caller]
-    fn peek_unchecked(&self) -> S::Ref<'static, T> {
-        self.inner.peek_unchecked()
+    fn try_peek_unchecked(&self) -> BorrowResult<S::Ref<'static, T>> {
+        self.inner.try_peek_unchecked()
     }
 }