Auto: ablegacy-5 — PD/MG/PLS/BT structure files

Adds PD (PID), MG (Message), PLS (Programmable Limit Switch) and BT
(Block Transfer) file types to the PCCC parser. New AbLegacyDataType
enum members (PidElement / MessageElement / PlsElement /
BlockTransferElement) plus per-type sub-element catalogue:

  - PD: SP/PV/CV/KP/KI/KD/MAXS/MINS/DB/OUT as Float32; EN/DN/MO/PE/
        AUTO/MAN/SP_VAL/SP_LL/SP_HL as Boolean (word-0 status bits).
  - MG: RBE/MS/SIZE/LEN as Int32; EN/EW/ER/DN/ST/CO/NR/TO as Boolean.
  - PLS: LEN as Int32 (bit table varies per PLC).
  - BT: RLEN/DLEN as Int32; EN/ST/DN/ER/CO/EW/TO/NR as Boolean.

Per-family flags on AbLegacyPlcFamilyProfile gate availability:

  - PD/MG: SLC500 + PLC-5 (operator + status bits both present).
  - PLS/BT: PLC-5 only (chassis-IO block transfer is PLC-5-specific).
  - MicroLogix + LogixPccc: rejected — no legacy file-letter form.

Status-bit indices match Rockwell DTAM / 1747-RM001 / 1785-6.5.12:
PD word 0 bits 0-8, MG/BT word 0 bits 8-15. PLC-set status bits
(PE/DN/SP_*; ST/DN/ER/CO/EW/NR/TO) are surfaced as ViewOnly via
IsPlcSetStatusBit, matching the Timer/Counter/Control pattern from
ablegacy-3.

LibplctagLegacyTagRuntime decodes PD non-bit members as Float32 and
MG/BT/PLS non-bit members as Int32; status bits route through GetBit
with the bit-position encoded by the driver via StatusBitIndex.

Tests: parser positive cases per family + negative cases per family,
catalogue + bit-index + read-only-bit assertions.

Closes #248

src/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/PlcFamilies/AbLegacyPlcFamilyProfile.cs

@@ -11,7 +11,11 @@ public sealed record AbLegacyPlcFamilyProfile(
     bool SupportsStringFile,
     bool SupportsLongFile,
     bool OctalIoAddressing,
-    bool SupportsFunctionFiles)
+    bool SupportsFunctionFiles,
+    bool SupportsPidFile,
+    bool SupportsMessageFile,
+    bool SupportsPlsFile,
+    bool SupportsBlockTransferFile)
 {
     public static AbLegacyPlcFamilyProfile ForFamily(AbLegacyPlcFamily family) => family switch
     {
@@ -29,7 +33,11 @@ public sealed record AbLegacyPlcFamilyProfile(
         SupportsStringFile: true,   // ST file available SLC 5/04+
         SupportsLongFile: true,     // L file available SLC 5/05+
         OctalIoAddressing: false,   // SLC500 I:/O: indices are decimal in RSLogix 500
-        SupportsFunctionFiles: false); // SLC500 has no function files
+        SupportsFunctionFiles: false, // SLC500 has no function files
+        SupportsPidFile: true,        // SLC 5/02+ supports PD via PID instruction
+        SupportsMessageFile: true,    // SLC 5/02+ supports MG via MSG instruction
+        SupportsPlsFile: false,       // SLC500 has no native PLS file (uses SQO/SQC instead)
+        SupportsBlockTransferFile: false); // SLC500 has no BT file (BT is PLC-5 ChassisIO only)
 
     public static readonly AbLegacyPlcFamilyProfile MicroLogix = new(
         LibplctagPlcAttribute: "micrologix",
@@ -38,7 +46,11 @@ public sealed record AbLegacyPlcFamilyProfile(
         SupportsStringFile: true,
         SupportsLongFile: false,    // ML 1100/1200/1400 don't ship L files
         OctalIoAddressing: false,   // MicroLogix follows SLC-style decimal I/O addressing
-        SupportsFunctionFiles: true); // ML 1100/1400 expose RTC/HSC/DLS/MMI/PTO/PWM/STI/EII/IOS/BHI
+        SupportsFunctionFiles: true, // ML 1100/1400 expose RTC/HSC/DLS/MMI/PTO/PWM/STI/EII/IOS/BHI
+        SupportsPidFile: false,       // MicroLogix 1100/1400 use PID-instruction-only addressing — no PD file type
+        SupportsMessageFile: false,   // No MG file — MSG instruction control words live in standard files
+        SupportsPlsFile: false,
+        SupportsBlockTransferFile: false);
 
     public static readonly AbLegacyPlcFamilyProfile Plc5 = new(
         LibplctagPlcAttribute: "plc5",
@@ -47,7 +59,11 @@ public sealed record AbLegacyPlcFamilyProfile(
         SupportsStringFile: true,
         SupportsLongFile: false,    // PLC-5 predates L files
         OctalIoAddressing: true,    // RSLogix 5 displays I:/O: word + bit indices as octal
-        SupportsFunctionFiles: false);
+        SupportsFunctionFiles: false,
+        SupportsPidFile: true,        // PLC-5 PID instruction needs PD file
+        SupportsMessageFile: true,    // PLC-5 MSG instruction needs MG file
+        SupportsPlsFile: true,        // PLC-5 has PLS (programmable limit switch) file
+        SupportsBlockTransferFile: true); // PLC-5 chassis I/O block transfer (BTR/BTW) needs BT file
 
     /// <summary>
     ///     Logix ControlLogix / CompactLogix accessed through the legacy PCCC compatibility layer.
@@ -61,7 +77,13 @@ public sealed record AbLegacyPlcFamilyProfile(
         SupportsStringFile: true,
         SupportsLongFile: true,
         OctalIoAddressing: false,   // Logix natively uses decimal arrays even via the PCCC bridge
-        SupportsFunctionFiles: false);
+        SupportsFunctionFiles: false,
+        // Logix native UDTs (PID_ENHANCED / MESSAGE) replace the legacy PD/MG file types — the
+        // PCCC bridge does not expose them as letter-prefixed files.
+        SupportsPidFile: false,
+        SupportsMessageFile: false,
+        SupportsPlsFile: false,
+        SupportsBlockTransferFile: false);
 }
 
 /// <summary>Which PCCC PLC family the device is.</summary>