feat(event_builder): expose scores_with_sigma fluent method

Adds EventBuilder::scores_with_sigma, the fluent-builder ergonomic
mirror of Outcome::scores_with_sigma. Lets users write
h.event(t).team(...).team(...).scores_with_sigma([..], sigma).commit()
to set a per-event score_sigma override.

src/event_builder.rs

@@ -81,6 +81,15 @@ where
         self
     }
 
+    /// Set explicit per-team continuous scores with a per-event noise override.
+    ///
+    /// `sigma` overrides `HistoryBuilder::score_sigma` for this event only.
+    /// Must be `> 0.0`; debug-asserts otherwise via `Outcome::scores_with_sigma`.
+    pub fn scores_with_sigma<I: IntoIterator<Item = f64>>(mut self, scores: I, sigma: f64) -> Self {
+        self.event.outcome = crate::Outcome::scores_with_sigma(scores, sigma);
+        self
+    }
+
     /// Mark team `winner_idx` as winner; others tied for last.
     pub fn winner(mut self, winner_idx: u32) -> Self {
         self.event.outcome = Outcome::winner(winner_idx, self.event.teams.len() as u32);