fix: populate story_name in event buffer via CRDT lookup

`subscribe_to_watcher` was pushing StoredEvents into the event
buffer with story_name hardcoded to String::new(), so /api/events
polled by the gateway always omitted the title. The 1035 fix
patched the other path (gateway_relay status_to_stored) but left
this one bleeding empty strings.

Lookup happens once at the subscriber boundary rather than at all
44 watcher emit sites — the story_id is already in hand and
crdt_state::read_item is the canonical name source.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/src/service/events/io.rs

@@ -31,9 +31,10 @@ pub fn subscribe_to_watcher(buffer: EventBuffer, mut rx: broadcast::Receiver<Wat
                     ..
                 }) => {
                     if let Some(from) = from_stage {
+                        let story_name = lookup_story_name(&item_id);
                         buffer.push(StoredEvent::StageTransition {
                             story_id: item_id,
-                            story_name: String::new(),
+                            story_name,
                             from_stage: from,
                             to_stage: stage,
                             timestamp_ms: now_ms(),
@@ -41,17 +42,19 @@ pub fn subscribe_to_watcher(buffer: EventBuffer, mut rx: broadcast::Receiver<Wat
                     }
                 }
                 Ok(WatcherEvent::MergeFailure { story_id, reason }) => {
+                    let story_name = lookup_story_name(&story_id);
                     buffer.push(StoredEvent::MergeFailure {
                         story_id,
-                        story_name: String::new(),
+                        story_name,
                         reason,
                         timestamp_ms: now_ms(),
                     });
                 }
                 Ok(WatcherEvent::StoryBlocked { story_id, reason }) => {
+                    let story_name = lookup_story_name(&story_id);
                     buffer.push(StoredEvent::StoryBlocked {
                         story_id,
-                        story_name: String::new(),
+                        story_name,
                         reason,
                         timestamp_ms: now_ms(),
                     });
@@ -68,3 +71,10 @@ pub fn subscribe_to_watcher(buffer: EventBuffer, mut rx: broadcast::Receiver<Wat
         }
     });
 }
+
+/// Look up the human-readable story name from the CRDT, or empty when absent.
+fn lookup_story_name(story_id: &str) -> String {
+    crate::crdt_state::read_item(story_id)
+        .map(|view| view.name().to_string())
+        .unwrap_or_default()
+}