fix(focas): decode servo/spindle meters by their base/exponent envelope; MaxRpm -> MotorSpeedPct

Servo (0x0056) and spindle (0x0040) meter records are 8 bytes:
[i32 value][u16 base][u16 exponent], the same self-describing envelope as the
position blocks.

Servo: offset 4 was read as a decimal count. It is the BASE (a steady 10), so
every load was divided by 10^10 and published ~0 -- the sister ignitionoee panel
read servo 0% on every axis of a Makino cutting at 20,000 rpm. Loads are now
value / base^exponent, a direct percentage.

Spindle: the raw meter is a 1/16384 fraction of full scale. Settled on the real
Z-34184 by regressing the type-1 meter against cnc_rddynamic2 spindle speed over
596..20,000 rpm (rpm = 1.220749 x meter; 16384 x 1.220749 = 20000.75). So:
- Spindle/{name}/Load publishes % of rated load (Float64; was the raw Int32
  count -- a reading of 9155 meant 55.9%).
- Spindle/{name}/MaxRpm is RENAMED Spindle/{name}/MotorSpeedPct (Float64, % of
  maximum speed) and is polled with Load. The old node was actively wrong: the
  type-1 meter is the live motor speed, and it was read once at bootstrap and
  served forever as if it were a max-RPM constant. Client-visible: FIXED: tags
  on .../MaxRpm must be re-pointed.
- The spindle read no longer stops at the first zero after slot 1 (which dropped
  an idle second spindle and kept non-zero residue); every slot is returned.

A record whose envelope is undescribable (base not 2/10, exponent > 18 -- e.g.
residue past the configured axis/spindle count) publishes BadNoData, never a Good 0.

Ported from the sister ignitionoee FOCAS driver v0.17.2/v0.17.3 (Focas.Wire-019);
live captures live-spmeter-{load,maxrpm}-0x0040.bin added as fixtures.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/Wire/WireFocasClient.cs

@@ -242,34 +242,32 @@ public sealed class WireFocasClient : IFocasClient
         var result = await _wire.ReadServoMeterAsync(32, cancellationToken).ConfigureAwait(false);
         if (!result.IsOk || result.Value is null) return [];
         return result.Value
-            .Select(m => new FocasServoLoad(m.Name ?? string.Empty, m.Value / Math.Pow(10.0, m.Decimal)))
+            .Select(m => new FocasServoLoad(m.Name ?? string.Empty, m.Scaled))
             .Where(s => s.AxisName.Length > 0)
             .ToList();
     }
 
     /// <inheritdoc />
-    public Task<IReadOnlyList<int>> GetSpindleLoadsAsync(CancellationToken cancellationToken) =>
+    public Task<IReadOnlyList<double?>> GetSpindleLoadsAsync(CancellationToken cancellationToken) =>
         ReadSpindleMetricAsync((sel, ct) => _wire.ReadSpindleLoadAsync(sel, ct), cancellationToken);
 
     /// <inheritdoc />
-    public Task<IReadOnlyList<int>> GetSpindleMaxRpmsAsync(CancellationToken cancellationToken) =>
-        ReadSpindleMetricAsync((sel, ct) => _wire.ReadSpindleMaxRpmAsync(sel, ct), cancellationToken);
+    public Task<IReadOnlyList<double?>> GetSpindleMotorSpeedsAsync(CancellationToken cancellationToken) =>
+        ReadSpindleMetricAsync((sel, ct) => _wire.ReadSpindleMotorSpeedAsync(sel, ct), cancellationToken);
 
-    private static async Task<IReadOnlyList<int>> ReadSpindleMetricAsync(
+    /// <summary>
+    ///     One <c>cnc_rdspmeter</c> read as per-slot percentages (null for an undescribable slot).
+    ///     Every slot is returned — the driver reads only the slots of discovered spindles. (This
+    ///     used to stop at the first zero after slot 1, which both dropped a genuinely idle second
+    ///     spindle and kept non-zero buffer residue.)
+    /// </summary>
+    private static async Task<IReadOnlyList<double?>> ReadSpindleMetricAsync(
         Func<short, CancellationToken, Task<FocasResult<IReadOnlyList<WireSpindleMetric>>>> call,
         CancellationToken cancellationToken)
     {
         var result = await call(-1, cancellationToken).ConfigureAwait(false);
         if (!result.IsOk || result.Value is null) return [];
-        var list = new List<int>();
-        foreach (var m in result.Value)
-        {
-            // Fanuc pads unused spindle slots with 0 — stop at the first trailing zero so the
-            // list length matches the configured spindle count.
-            if (m.Value == 0 && list.Count > 0) break;
-            list.Add(m.Value);
-        }
-        return list;
+        return result.Value.Select(m => m.Percent).ToList();
     }
 
     /// <summary>Disposes the wire client and releases all resources.</summary>