[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]

• P1 — OTel bypasses applications’ custom CDI HTTP client: createPropagatingClient is an enabled alternative, so it wins CDI resolution over an application’s normal A2AHttpClient bean. It then deliberately excludes the cdi provider and wraps a built-in JDK/Vert.x client instead. This breaks the documented CDI customization path—for example, custom mTLS, proxy, authentication, or timeouts are silently ignored for push delivery whenever the OTel server extra is present. The propagating client needs to wrap the user-selected client rather than replace it (or use an explicit qualifier/configuration to avoid changing default selection).