Auto: focas-f1f — figure scaling + diagnostics

Closes #262

src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriverOptions.cs

@@ -11,6 +11,34 @@ public sealed class FocasDriverOptions
     public IReadOnlyList<FocasTagDefinition> Tags { get; init; } = [];
     public FocasProbeOptions Probe { get; init; } = new();
     public TimeSpan Timeout { get; init; } = TimeSpan.FromSeconds(2);
+
+    /// <summary>
+    ///     Fixed-tree behaviour knobs (issue #262, plan PR F1-f). Carries the
+    ///     <c>ApplyFigureScaling</c> toggle that gates the <c>cnc_getfigure</c>
+    ///     decimal-place division applied to position values before publishing.
+    /// </summary>
+    public FocasFixedTreeOptions FixedTree { get; init; } = new();
+}
+
+/// <summary>
+///     Per-driver fixed-tree options. New installs default <see cref="ApplyFigureScaling"/>
+///     to <c>true</c> so position values surface in user units (mm / inch). Existing
+///     deployments that already published raw scaled integers can flip this to <c>false</c>
+///     for migration parity — the operator-facing concern is that switching the flag
+///     mid-deployment changes the values clients see, so the migration path is
+///     documentation-only (issue #262).
+/// </summary>
+public sealed record FocasFixedTreeOptions
+{
+    /// <summary>
+    ///     When <c>true</c> (default), position values from <c>cnc_absolute</c> /
+    ///     <c>cnc_machine</c> / <c>cnc_relative</c> / <c>cnc_distance</c> /
+    ///     <c>cnc_actf</c> are divided by <c>10^decimalPlaces</c> per axis using the
+    ///     <c>cnc_getfigure</c> snapshot cached at probe time. When <c>false</c>, the
+    ///     raw integer values are published unchanged — used for migrations from
+    ///     older drivers that didn't apply the scaling.
+    /// </summary>
+    public bool ApplyFigureScaling { get; init; } = true;
 }
 
 /// <summary>