fix(ablegacy): final review I3 — default reverts to libplctag; Native is opt-in

On a wire the native PCCC path is proven only for N-file reads/writes and
one F8 read (ab_server). An absent transport key now resolves to Libplctag
for every family; explicit Native still wins and still warns once per
instance on PLC-5/LogixPccc. AdminUI dropdown, CLI help, evidence claims
(PcccFileType, AbLegacy.md wire-evidence table, release note) corrected:
S:0 (default probe) and B/T/C/R/S/L/ST/A/O/I are unverified natively.

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

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport/Pccc/PcccFileType.cs

@@ -1,8 +1,13 @@
 namespace ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Pccc;
 
 /// <summary>PCCC file-type codes for the protected typed logical read/write commands (0xA2/0xAA).
-/// N (0x89) and F (0x8A) are verified against the golden captures; the rest follow the PCCC
-/// data-table file-type table.</summary>
+/// <para>Wire evidence (final review I3), all against the <c>ab_server</c> simulator, never a real PLC:
+/// N (0x89) — byte parity with libplctag captures (SLC 500 read + write, MicroLogix read, PLC-5 read) and
+/// native ab_server round trips (N7:0 read on all three profiles, N7:5 write on SLC 500); F (0x8A) — one
+/// SLC 500 F8 read capture only (no native write on a wire).</para>
+/// <para>S, B, T, C, R, ST, A, L, O and I are encoded from the PCCC data-table file-type table and are
+/// UNVERIFIED natively — no capture and no simulator test. That includes S:0, the default probe address,
+/// and the T/C/R sub-element (PRE/ACC/LEN/POS) word offsets.</para></summary>
 public static class PcccFileType
 {
     /// <summary>Returns the file-type code for a file letter (case-insensitive), or null when unknown.</summary>