fix(historian): T10 review — tick-exact bucketing over the full DateTime range; AtTime outage keeps its Bad code

Important 1: bucket offsets are now 100 ns ticks as bigint
(DATEDIFF_BIG(microsecond)*10 plus the sub-microsecond tick digits), so a
1601→9999 window no longer overflows (SQL 535) and nothing scales the interval
to nanoseconds in C#. Interval wider than the window clamps to one bucket and
the ceiling division cannot overflow. Exactness to the tick is unchanged.

Important 2 (spec §4 ruling d6afb394): a Bad previous neighbour means the time
is inside an outage — null value with that neighbour's Bad code, never
Uncertain. Usable previous + Bad next still holds the previous value Uncertain.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer/SqlAggregateQueries.cs

@@ -18,17 +18,21 @@ internal enum SqlAggregateFamily
 /// <summary>
 ///     Push-down T-SQL for processed (aggregate) reads (spec §4 "Processed"). Every query takes
 ///     <c>@id</c> (int TagId), <c>@start</c>/<c>@end</c> (<c>datetime2(7)</c>, the forward window
-///     <c>[start, end)</c>) and <c>@intervalNs</c> (bigint bucket width in nanoseconds), and returns one row
+///     <c>[start, end)</c>) and <c>@intervalTicks</c> (bigint bucket width in 100 ns ticks), and returns one row
 ///     per <b>non-empty</b> bucket. The caller generates every interval and fills the empty ones.
 /// </summary>
 /// <remarks>
 ///     <para>
-///         <b>Bucketing.</b> <c>b = DATEDIFF_BIG(nanosecond, @start, SourceTimeUtc) / @intervalNs</c>. The spec
-///         sketched <c>millisecond</c>, but <c>DATEDIFF</c> counts unit <i>boundaries crossed</i>, not elapsed
-///         time, so with a non-millisecond-aligned <c>@start</c> a sample one tick before a bucket edge would
-///         land in the next bucket. <c>datetime2(7)</c> values are whole multiples of 100 ns, so the nanosecond
-///         boundary count IS the exact elapsed time and the integer division gives start-inclusive /
-///         end-exclusive buckets to the tick. (Range limit: ≈292 years per window.)
+///         <b>Bucketing.</b> <c>b = elapsedTicks / @intervalTicks</c>, where
+///         <c>elapsedTicks = DATEDIFF_BIG(microsecond, @start, t) * 10 + tick-of-microsecond(t) − tick-of-microsecond(@start)</c>
+///         and <c>tick-of-microsecond(x) = (DATEPART(nanosecond, x) / 100) % 10</c>. The spec sketched
+///         <c>millisecond</c>, but <c>DATEDIFF</c> counts unit <i>boundaries crossed</i>, not elapsed time, so with a
+///         non-millisecond-aligned <c>@start</c> a sample one tick before a bucket edge would land in the next
+///         bucket. Counting microsecond boundaries and correcting by the two sub-microsecond tick digits gives
+///         the exact elapsed time in 100 ns ticks (10·(⌊t/10⌋ − ⌊s/10⌋) + t mod 10 − s mod 10 = t − s), so the
+///         integer division is start-inclusive / end-exclusive to the tick. Unlike a nanosecond <c>DATEDIFF_BIG</c>
+///         (which overflows a bigint past ≈292 years, SQL error 535), the microsecond count over the whole
+///         <c>datetime2</c> range (0001–9999, ≈3.2e17 µs, ≈3.2e18 ticks) fits a bigint.
 ///     </para>
 ///     <para>
 ///         <b>Sample classes</b> (status stored bit-for-bit in an <c>int</c>, so the severity bits are the sign
@@ -114,7 +118,8 @@ internal static class SqlAggregateQueries
 
     /// <summary>The <c>s</c> CTE: the window's samples with bucket index and the usable/good flags.</summary>
     private static string Classified(string sample) =>
-        "WITH s AS (SELECT DATEDIFF_BIG(nanosecond, @start, SourceTimeUtc) / @intervalNs AS b, " +
+        "WITH s AS (SELECT (DATEDIFF_BIG(microsecond, @start, SourceTimeUtc) * 10 " +
+        "+ (DATEPART(nanosecond, SourceTimeUtc) / 100) % 10 - (DATEPART(nanosecond, @start) / 100) % 10) / @intervalTicks AS b, " +
         "SourceTimeUtc, ValueKind, NumValue, IntValue, StrValue, " +
         "CASE WHEN StatusCode >= 0 AND ValueKind <> 0 THEN 1 ELSE 0 END AS u, " +
         "CASE WHEN StatusCode >= 0 AND StatusCode < 1073741824 AND ValueKind <> 0 THEN 1 ELSE 0 END AS g " +