[ehsavoie]

• Add OpenTelemetryPushNotificationSenderDecorator with CLIENT spans that reflect actual delivery outcome (OK on success, ERROR on failure)
• Add OpenTelemetryA2AHttpClient to inject W3C traceparent/tracestate headers into outbound push notification HTTP requests
• Change PushNotificationSender.sendNotification() from void to boolean so decorators can observe delivery success or failure
• Use @Alternative @priority(1) to resolve CDI ambiguity on A2AHttpClient
• DRY: merge extractTaskId/extractContextId into single extractIds()
• Fix null safety in span error description
• Remove LENIENT Mockito strictness, stub only in tests that need it
• Refactor integration test helpers: shared HttpClient, Gson, clearExportedSpans()
• Use HashMap instead of ConcurrentHashMap where CopyOnWriteArrayList suffices

Fixes #1217 🦕

[ehsavoie]

Supersedes #1228

[kabir]

• P2 — Custom dispatch executors cannot override the default: OpenTelemetryHttpClientProducer.java:112 produces a normal-scoped @nAmed("a2a.pushNotificationDispatch") Executor. If an application follows the documented override approach and defines its own executor with that name, CDI sees two matching beans. Consequently, BasePushNotificationSender.java:123 finds the Instance ambiguous (isResolvable() == false) and silently falls back to the common pool. This defeats the advertised override and loses trace-context propagation. Use an explicit override mechanism (for example specialization or a documented alternative/priority scheme), and add an integration test with a user-provided named executor.