Address Copilot PR feedback: BrokerRequest Javadoc + result adapter exception handling

- BrokerRequest.mOnboardingSeedJson: clarify direction is client -> broker only;
  the broker returns the populated blob via BrokerResult.getOnboardingBlob(),
  not by mutating this seed field.
- MsalBrokerResultAdapter.getAcquireTokenResultFromResultBundle: catch
  ClientException specifically (the only declared exception from
  brokerResultFromBundle) instead of swallowing all Exception, log at warn
  level so IPC/regression issues remain diagnosable, and remove the redundant
  null check (brokerResultFromBundle is non-null or throws). Blob contents are
  not logged (may carry sessionCorrelationId).

Author: wzhipan

common/src/main/java/com/microsoft/identity/common/internal/broker/BrokerRequest.java

@@ -299,8 +299,12 @@ private static final class SerializedNames {
 
     /**
      * Onboarding telemetry seed JSON blob.
-     * Contains sessionCorrelationId, onboarding_mode, schema_version.
-     * Broker populates this with blocking errors and returns in the result.
+     * Direction: client → broker (input only). Contains sessionCorrelationId,
+     * onboarding_mode, and schema_version, supplied by the client (OneAuth/MSAL)
+     * so the broker can construct an OnboardingTelemetryRecorder using the same
+     * correlation id. The broker returns the populated blob (with steps and
+     * blocking errors) via {@link BrokerResult#getOnboardingBlob()}, not via
+     * this field.
      */
     @Nullable
     @SerializedName(SerializedNames.ONBOARDING_SEED_JSON)

common/src/main/java/com/microsoft/identity/common/internal/result/MsalBrokerResultAdapter.java

@@ -1015,6 +1015,7 @@ public AcquireTokenResult getDeviceCodeFlowTokenResultFromResultBundle(@NonNull
 
     public @NonNull
     AcquireTokenResult getAcquireTokenResultFromResultBundle(@NonNull final Bundle resultBundle) throws BaseException {
+        final String methodTag = TAG + ":getAcquireTokenResultFromResultBundle";
         final MsalBrokerResultAdapter resultAdapter = new MsalBrokerResultAdapter();
         if (resultBundle.getBoolean(AuthenticationConstants.Broker.BROKER_REQUEST_V2_SUCCESS)) {
             final AcquireTokenResult acquireTokenResult = new AcquireTokenResult();
@@ -1039,14 +1040,17 @@ AcquireTokenResult getAcquireTokenResultFromResultBundle(@NonNull final Bundle r
                 );
             }
 
-            // Extract onboarding blob from BrokerResult if present
+            // Extract onboarding blob from BrokerResult if present. Best-effort — telemetry
+            // failures must never fail an otherwise-successful auth result. Logged at warn so
+            // diagnosing IPC/regression issues remains possible. Blob contents are not logged
+            // (may contain sessionCorrelationId).
             try {
                 final BrokerResult brokerResult = resultAdapter.brokerResultFromBundle(resultBundle);
-                if (brokerResult != null && brokerResult.getOnboardingBlob() != null) {
+                if (brokerResult.getOnboardingBlob() != null) {
                     acquireTokenResult.setOnboardingBlob(brokerResult.getOnboardingBlob());
                 }
-            } catch (final Exception e) {
-                // Best-effort — don't fail the result for telemetry
+            } catch (final ClientException e) {
+                Logger.warn(methodTag, "Failed to extract onboarding blob from broker result: " + e.getErrorCode());
             }
 
             return acquireTokenResult;