feat(telemetry): correlate consensus doAccept logs via non-owning span activation

Activate the accept span as ambient context at the top of doAccept using the
non-owning ScopedActivation, so doAccept's log lines (and any spans created in
the body) carry the accept span's trace_id. doAccept runs to completion on the
JtAccept worker with no coroutine yield, so the activation is thread-local and
safe; the acceptSpan still owns and ends the span. The accept.apply child span
keeps its explicit childSpan(acceptApply, acceptSpanContext_) parentage --
activation only adds log correlation and does not alter parent linkage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/xrpld/app/consensus/RCLConsensus.cpp

@@ -556,6 +556,13 @@ RCLConsensus::Adaptor::doAccept(
 {
     namespace cs = telemetry::consensus::span;
 
+    // Make the accept span ambient for the whole accept so doAccept's log lines
+    // (and any spans created here) correlate to it. Non-owning: acceptSpan still
+    // owns/ends the span. doAccept runs to completion on the JtAccept worker
+    // (no coroutine yield), so this scope is thread-local and safe.
+    auto acceptActivation =
+        (acceptSpan && *acceptSpan) ? acceptSpan->activate() : telemetry::ScopedActivation{};
+
     prevProposers_ = result.proposers;
     prevRoundTime_ = result.roundTime.read();