docs(telemetry): drop PR-internal history from the new comments

A comment that describes an earlier state of its own branch documents something
no reader can look up, because the branch is squash-merged and the state it
contrasts against never reaches the merged history. Four passages in
HistogramBuckets.h and one in Telemetry.cpp did exactly that, and the
OTelCollector and Unit.h wording implied a transition rather than a fact.

- HistogramBuckets.h: the ladders now explain the invariant they enforce,
  instead of recounting where the edges used to live and how they drifted.
- Telemetry.cpp: one view per unit means a byte count is bucketed on the byte
  ladder, stated directly rather than as something it stopped inheriting.
- OTelCollector.cpp: the collector is described by what it is, a thin adapter
  over the shared pipeline, rather than as a shim that gave up an exporter.
- Unit.h: the StatsD path is out of service as a present fact, and the contract
  its wire format would break is an external protocol one.

Comment text only. No declaration, signature or emitted value changes.

include/xrpl/beast/insight/Unit.h

@@ -20,11 +20,11 @@ namespace beast::insight {
  *     makeEvent("time", Unit::Millis) --> OTel unit "ms" --> millisecond ladder
  *     makeEvent("size", Unit::Bytes)  --> OTel unit "By" --> byte ladder
  *
- * The StatsD backend deliberately ignores this and keeps emitting `|ms` for
- * every Event. That path is retired here -- its UDP port is commented out of
- * the compose file and the integration test fails if anything is listening on
- * 8125 -- so changing its wire format would alter a legacy contract for no
- * local benefit and with no way to verify it.
+ * The StatsD backend deliberately ignores this and emits `|ms` for every
+ * Event. That path is out of service -- its UDP port is commented out of the
+ * compose file and the integration test fails if anything is listening on
+ * 8125 -- so changing its wire format would alter an external protocol
+ * contract for no local benefit and with no way to verify it.
  *
  * @note Adding a member requires extending otelUnitCode(), which switches
  *       exhaustively so a new member is a compile error rather than a silent

include/xrpl/telemetry/HistogramBuckets.h

@@ -11,10 +11,8 @@ namespace xrpl::telemetry::buckets {
  * @file HistogramBuckets.h
  * @brief Explicit histogram bucket edges for xrpld's OTel instruments.
  *
- * One header owns every ladder so a reviewer sees all of them at once and a
- * test can assert their invariants. Before this existed the edges lived as
- * file-local `namespace {}` constants, unreachable from any test, and they
- * drifted apart.
+ * One header owns every ladder, so a reviewer sees all of them together and
+ * a test can assert their invariants.
  *
  * Why a ladder is worth this much care: when a quantile falls in the `+Inf`
  * bucket, Prometheus returns the *second-highest* edge, not `+Inf`. A
@@ -68,11 +66,10 @@ namespace xrpl::telemetry::buckets {
  * **This list must contain every representable edge of the collector's
  * spanmetrics ladder, and may extend above it.** Agreement over the shared
  * range is deliberate: it lets a span-derived latency panel and a native
- * histogram panel be read on the same scale. It was specified that way
- * originally, then silently broken when the collector ladder alone was
- * extended, which left this side capped at 5 s while spans reached 30 s and
- * censored every quantile above 5 s. `check_bucket_parity.py` now enforces
- * the containment -- add a collector edge, add it here too.
+ * histogram panel be read on the same scale. Drop an edge the collector
+ * carries and every quantile above it reads back as the top edge instead of
+ * failing. `check_bucket_parity.py` enforces the containment -- add a
+ * collector edge, add it here too.
  *
  * The sub-millisecond edges the collector carries (0.01 to 0.5 ms) are
  * deliberately absent. `beast::insight::Event` rounds every duration up to
@@ -86,8 +83,8 @@ namespace xrpl::telemetry::buckets {
  * as 5 s censors them today. All these Events share one ladder, so its
  * ceiling has to cover the slowest member rather than the typical one.
  *
- * The 2, 3 and 4 s edges resolve second-scale work that previously had to
- * interpolate across a single four-second-wide bucket.
+ * The 2, 3 and 4 s edges resolve second-scale work, which a single
+ * four-second-wide bucket can only interpolate across.
  */
 inline constexpr std::array kMillisecondBuckets{
     1.0,

src/libxrpl/beast/insight/OTelCollector.cpp

@@ -4,10 +4,9 @@
  *
  * Compiled only when XRPL_ENABLE_TELEMETRY is defined (via CMake
  * telemetry=ON). Maps beast::insight instruments to OTel SDK instruments
- * created on the GLOBAL Meter published by the telemetry module. This class
- * is a legacy shim: it no longer owns an export pipeline. The MeterProvider,
- * PeriodicExportingMetricReader, OTLP exporter and histogram view all live in
- * xrpl::telemetry::Telemetry.
+ * created on the GLOBAL Meter published by the telemetry module. It owns no
+ * export pipeline of its own: the MeterProvider, PeriodicExportingMetricReader,
+ * OTLP exporter and histogram view all live in xrpl::telemetry::Telemetry.
  *
  * When XRPL_ENABLE_TELEMETRY is not defined, OTelCollector::New() returns
  * a NullCollector so the build succeeds without OTel dependencies.
@@ -380,7 +379,7 @@ private:
 //------------------------------------------------------------------------------
 
 /**
- * @brief Main OTel Collector implementation (legacy shim).
+ * @brief Main OTel Collector implementation.
  *
  * Obtains its Meter from the GLOBAL MeterProvider owned and published by the
  * telemetry module (xrpl::telemetry::Telemetry), rather than building its own
@@ -389,7 +388,7 @@ private:
  *
  * The metrics pipeline (MeterProvider + PeriodicExportingMetricReader + OTLP
  * HTTP exporter + histogram view) lives in the telemetry module. This class is
- * a thin adapter kept for beast::insight callers during deprecation.
+ * the thin adapter that lets beast::insight callers reach it.
  *
  * Class diagram:
  *
@@ -445,10 +444,10 @@ public:
      *
      * @param endpoint    OTLP/HTTP metrics endpoint URL. Informational only:
      *                    the global telemetry pipeline is authoritative for
-     *                    the actual export endpoint. Retained for logging and
-     *                    back-compat with the New() signature.
-     * @param prefix      Legacy metric-name prefix. Not applied to metric
-     *                    names; used only in the startup log line.
+     *                    the actual export endpoint. Used only in the startup
+     *                    log line.
+     * @param prefix      Metric-name prefix. Not applied to metric names;
+     *                    used only in the startup log line.
      * @param instanceId  Value for the service.instance.id resource attribute.
      *                    When empty, the attribute is omitted.
      * @param serviceName Value for the service.name resource attribute.

src/libxrpl/telemetry/Telemetry.cpp

@@ -408,9 +408,9 @@ class TelemetryImpl : public Telemetry
         meterProvider_->AddMetricReader(std::move(reader));
 
         // One histogram view per unit. The unit is the selector, so an
-        // instrument gets the ladder that fits what it measures -- a byte
-        // count no longer inherits a latency ladder. Edges come from
-        // HistogramBuckets.h, which owns every ladder.
+        // instrument gets the ladder that fits what it measures: a byte count
+        // is bucketed on the byte ladder and never on a latency one. Edges
+        // come from HistogramBuckets.h, which owns every ladder.
         //
         // Both views keep the "*" name pattern and an EMPTY view name: a
         // non-empty view name would rename every matching histogram to it and