docs: fix 10 rustdoc link warnings, deny broken/private/redundant intra-doc links, doctests deny(warnings) (3 doctests had unused vars/imports)

src/scheduler.rs

@@ -263,6 +263,7 @@ impl Drop for JoinHandle {
 /// ```
 /// use smarm::SpawnOpts;
 /// let opts = SpawnOpts { stack_reserve: Some(8 * 1024 * 1024), ..SpawnOpts::default() };
+/// assert_eq!(opts.stack_reserve, Some(8 * 1024 * 1024));
 /// ```
 ///
 /// Both sizes are page-rounded. The reserve is *virtual* (demand-paged):
@@ -286,8 +287,8 @@ pub struct SpawnOpts {
 #[non_exhaustive]
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum SpawnError {
-    /// The fixed actor slab ([`Config::max_actors`]
-    /// (crate::runtime::Config::max_actors)) is full: every slot is claimed
+    /// The fixed actor slab ([`Config::max_actors`](crate::runtime::Config::max_actors))
+    /// is full: every slot is claimed
     /// by a live actor. This is a routine overload condition, not an
     /// invariant violation — shed the unit of work (close the socket,
     /// return a 503) and try again once actors have died.
@@ -371,7 +372,7 @@ pub fn spawn_under_with<A>(
     }
 }
 
-/// [`spawn`] and [`monitor`](crate::monitor) the child in one step, with no
+/// [`spawn`] and [`monitor`](crate::monitor()) the child in one step, with no
 /// window in which the child can die unobserved.
 ///
 /// `spawn` followed by `monitor(h.pid())` races: on a multi-scheduler