Auto: focas-f2a — DIAG: address scheme

New FocasAreaKind.Diagnostic parsed from DIAG:nnn (whole-CNC) and
DIAG:nnn/axis (per-axis), validated against a per-series
FocasCapabilityMatrix.DiagnosticRange table (16i: 0-499; 0i-F family:
0-999; 30i/31i/32i: 0-1023; Power Motion i: 0-255; Unknown: permissive
per existing matrix convention).

IFocasClient gains ReadDiagnosticAsync(diagNumber, axisOrZero, type,
ct) with a default returning BadNotSupported so older transport
variants degrade gracefully. FwlibFocasClient implements it via a new
cnc_rddiag P/Invoke that reuses the IODBPSD struct (same shape as
cnc_rdparam). FocasDriver.ReadAsync dispatches Diagnostic addresses
through the new path; non-Diagnostic kinds keep the existing
ReadAsync route unchanged.

Tests: parser positives (DIAG:1031, DIAG:280/2, case-insensitive,
zero, axis-8) + negatives (malformed, axis>31), capability matrix
boundaries per series, driver-level dispatch verifying axis index
threads through, init-time rejection on out-of-range, and
BadNotSupported fallback when the wire client doesn't override the
default. 266/266 pass in Driver.FOCAS.Tests.

Closes #263

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -58,7 +58,8 @@ public sealed record FocasDeviceOptions(
 /// <summary>
 ///     One FOCAS-backed OPC UA variable. <paramref name="Address"/> is the canonical FOCAS
 ///     address string that parses via <see cref="FocasAddress.TryParse"/> —
-///     <c>X0.0</c> / <c>R100</c> / <c>PARAM:1815/0</c> / <c>MACRO:500</c>.
+///     <c>X0.0</c> / <c>R100</c> / <c>PARAM:1815/0</c> / <c>MACRO:500</c> /
+///     <c>DIAG:1031</c> / <c>DIAG:280/2</c>.
 /// </summary>
 public sealed record FocasTagDefinition(
     string Name,