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

Two conflicts, both additive-vs-additive; each resolution keeps both sides.

check_otel_naming.py -- phase-10 taught the L6 label extractor to match the
label MAP first and to resolve a key hoisted into a `k...Label` constant,
scanning headers as well as sources. Our side had added the two-regex
first/subsequent literal scan and the `metric_constants(root)[1]` union that
covers the `namespace label` header style.

Kept phase-10's mechanism whole: METRIC_LABEL_MAP + the `(?:^|\{)` key regex
already subsumes what METRIC_LABEL_NEXT did, since matching inside the map body
makes every pair after the first open with a single `{`. So METRIC_LABEL_NEXT is
dropped as genuinely redundant rather than kept as a duplicate scan, and the
reason it existed is folded into METRIC_LABEL's comment. Re-added our
`metric_constants(root)[1]` union on top: LABEL_CONST_DEF only matches
`k`-prefixed identifiers, so it cannot see MetricNames.h's `label::jobType`
style, and without that union Rule D would reject dashboards querying labels
Rule I forced into constants. The two derivations are complementary and both
are now documented as such.

MetricsRegistry.cpp -- both sides added a new sibling view-registration helper
next to addMicrosecondHistogramView, and both added a registration call in
initExporterAndProvider(). Kept all four helpers
(addHistogramView/Microsecond/RoundDuration/SubMillisecond) and every
registration: phase-10's addSubMillisecondHistogramView + kNodeStoreReadUs
alongside our addRoundDurationHistogramView, sweepMallocTrimUs and the two
millisecond dial/resolve ladders.

phase-10's nodestore_read_us histogram does not duplicate our work. The
nodestore_latency gauge that would have overlapped it was retired in c4e434d520
before this merge, and the surviving nodestore_state gauge is complementary
rather than duplicative: both read the same fetch measurement, but the gauge
publishes only a since-boot mean via scaledMean() and cannot yield a
percentile -- the consequence observeNodeStoreTotals' own docs state plainly --
while the histogram buckets each fetch and can. The histogram also splits by
fetch_type and found, which the gauge cannot. phase-10 registered its
explicit-bucket View, so it does not inherit the SDK default ladder.

Each file keeps its own existing naming style: phase-10's k-prefixed constants
are left as-is, ours stay namespaced.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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

@@ -140,7 +140,6 @@ test.nodestore > xrpl.basics
 test.nodestore > xrpl.config
 test.nodestore > xrpld.core
 test.nodestore > xrpl.nodestore
-test.nodestore > xrpl.protocol
 test.nodestore > xrpl.rdb
 test.overlay > test.jtx
 test.overlay > test.unit_test