merge: bring phase10-workload-validation forward into sync-diagnostics

Resolutions:
- MetricsRegistry.cpp: keep both <exception> and <limits>; drop
  incrementStateChanges(), which this branch removed on purpose (the
  labelled state_changes_total call site in NetworkOPsImp::setMode
  replaces it, and a compile-time test guards that).
- tests/MetricsRegistry.cpp: constructor-built pipeline wording from
  phase-10, this branch's test list and gauge paragraphs kept; the two
  lifecycle tests now call startAsyncGauges() and pass kTestOptions.
- tests/MetricMacros.cpp: comments name the recording() gate.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.github/scripts/levelization/results/ordering.txt

@@ -203,6 +203,7 @@ tests.libxrpl > xrpl.nodestore
 tests.libxrpl > xrpl.peerfinder
 tests.libxrpl > xrpl.protocol
 tests.libxrpl > xrpl.protocol_autogen
+tests.libxrpl > xrpl.rdb
 tests.libxrpl > xrpl.resource
 tests.libxrpl > xrpl.server
 tests.libxrpl > xrpl.shamap

.github/scripts/telemetry/test_check_regression_bounds.py

@@ -247,7 +247,7 @@ class TestRules(CheckerCase):
         """A hand-edited bound that is a string must be named, not raise."""
         self.edit_json(
             THRESHOLDS,
-            lambda d: d["overrides"]["span.ledger.build"]["p99"].update(
+            lambda d: d["overrides"]["span.ledger.build"]["p95"].update(
                 max_abs_increase_ms="5.5"
             ),
         )