Lighten the comment load

Drops porting-history narratives (dodrenett), superseded-behavior
explanations, and restatements of what the next line does. Constraint
notes (fail-closed policies, CAS semantics, cascade behavior, id
uniqueness) stay, just shorter. No code changes.

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

src/aggregates/mod.rs

@@ -174,10 +174,8 @@ pub enum TransitionError {
     /// No creation event found for this id - nothing to transition.
     UnknownAggregate,
     DisallowedTransition { from: String, to: String },
-    /// A concurrent writer already advanced this aggregate past the
-    /// sequence this call read - the fix for the lost-update race
-    /// `answers::transition_answer` used to have (see
-    /// `crate::events::store::append_event`'s CAS).
+    /// A concurrent writer advanced this aggregate past the sequence
+    /// this call read (see `events::store::append_event`'s CAS).
     Conflict,
     Store(String),
 }