Merge branch 'pratik/otel-phase10-workload-validation' into pratik/otel-sync-diagnostics

expected_spans.json: composed both sides. Kept this branch's 16 extra spans,
relationships and the per_ledger join group; took phase-10's allowed_parents
gate for the shared entries and derived allowed_parents for the 16 from their
factories. ledger.store, ledger.validate and ledger.acquire are hashSpan roots
on this branch, so they list ROOT alone rather than consensus.accept.apply.

include/xrpl/consensus/ConsensusSpanNames.h

@@ -59,7 +59,9 @@
  *    |     Attrs:   proposers, round_time_ms, quorum
  *    |   |
  *    |   +-- consensus.accept.apply              [jtACCEPT thread, child of accept]
- *    |         Created: Adaptor::doAccept()
+ *    |         Created: Adaptor::doAccept(), scoped: the txq spans doAccept
+ *    |                  goes on to create nest under it; the tx apply-stage
+ *    |                  spans are hash-derived roots and do not
  *    |     Attrs:   ledger_seq, close_time_ripple_epoch_s, close_time_correct,
  *    |              close_resolution_ms, consensus_state, proposing, round_time_ms,
  *    |              parent_close_time_ripple_epoch_s, close_time_self_ripple_epoch_s,
@@ -71,7 +73,7 @@
  *    |     Attrs:   ledger_seq, proposing
  *    |
  *    +-- consensus.mode_change                   [main thread]
- *          Created: Adaptor::onModeChange()
+ *          Created: Adaptor::onModeChange(), only when the mode moves
  *          Attrs:   mode_old, mode_new
  *
  *  Standalone spans (no parent, created per-message in overlay):

include/xrpl/telemetry/SpanGuard.h

@@ -918,6 +918,15 @@ public:
     void
     addEvent(std::string_view name) noexcept;
 
+    /**
+     * Add a named event with key-value attributes to the span's timeline.
+     * No-op on a null guard.
+     * @param name   Event name.
+     * @param attrs  Attribute pairs (all string_view for simplicity).
+     */
+    void
+    addEvent(std::string_view name, std::initializer_list<EventAttribute> attrs) noexcept;
+
     /**
      * Record an exception as a span event and mark status as error.
      * No-op on a null guard.
@@ -1355,6 +1364,10 @@ public:
     {
     }
     void
+    addEvent(std::string_view, std::initializer_list<EventAttribute>) noexcept
+    {
+    }
+    void
     recordException(std::exception const&) noexcept
     {
     }