fix(client): contain notification-callback failures and document the source lifecycle

Review follow-ups: the three new notify loops (currentProvideInfo
subscribers, ui-skill lexicon listeners, late-registration controller
setup) now contain per-callback failures so one faulty consumer cannot
starve the rest, abort the list projection pass, or poison the source
roster with no disposer; controller lexicon polling drops a throwing
source with a console record like the candidate path. The ui-slash
README (both languages) now states the late-registration warm and the
subscribeLexicon contract, and the scenario suite drives a typed /name
token gaining its decoration when the roll settles with no further
input.

packages/client/ui-skill/src/client/index.ts

@@ -48,7 +48,16 @@ export function apply(ctx: ClientContext): void {
   const lexiconListeners = new Map<SessionId, Set<() => void>>()
 
   const notifyLexicon = (sessionId: SessionId): void => {
-    for (const listener of [...(lexiconListeners.get(sessionId) ?? [])]) listener()
+    for (const listener of [...(lexiconListeners.get(sessionId) ?? [])]) {
+      try {
+        listener()
+      } catch (error) {
+        // Contain listener failures: settlement notifies from an ignored
+        // promise chain (a throw would surface as an unhandled rejection)
+        // and one faulty consumer must not starve the others.
+        console.error('[ui-skill] lexicon listener failed:', error)
+      }
+    }
   }
 
   const fetchCatalog = (sessionId: SessionId): Promise<readonly SkillEntry[]> => {