feat: redesign bench calibration (factor/offset), add Ttank/P2 displays, fix sensor calibration

- Replace P1-P6 rational transfer function with factor/offset model for bench params
- Add explicit rx/tx direction flags in bench XML configuration
- Add T.Tank (BenchTemp) and P2 (AnalogSensor2) to temperature/pressure display
- Apply SensorConfiguration calibration to pressure channels, fix empty sensors.xml fallback
- Add live value labels to flowmeter charts
- Hide pump live values and PSG encoder standalone label
- Add K-Line connection state model, improve KWP service and status displays
- Restructure .claude/skills into subdirectory format

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Services/IKwpService.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
+using HC_APTBS.Models;
 
 namespace HC_APTBS.Services
 {
@@ -11,6 +12,31 @@ namespace HC_APTBS.Services
     /// </summary>
     public interface IKwpService
     {
+        // ── Session lifecycle ─────────────────────────────────────────────────────
+
+        /// <summary>Current state of the persistent K-Line session.</summary>
+        KLineConnectionState KLineState { get; }
+
+        /// <summary>
+        /// Raised whenever the K-Line session state transitions.
+        /// Fires on a background thread; consumers must marshal to the UI thread.
+        /// </summary>
+        event Action<KLineConnectionState>? KLineStateChanged;
+
+        /// <summary>
+        /// Opens a persistent K-Line session: performs 5-baud slow-init,
+        /// reads ECU info, then starts a background keep-alive loop (~1 s interval).
+        /// </summary>
+        /// <param name="port">FTDI serial number or COM port identifier.</param>
+        /// <param name="ct">Cancellation token.</param>
+        Task ConnectAsync(string port, CancellationToken ct = default);
+
+        /// <summary>
+        /// Stops the keep-alive loop, sends EndCommunication to the ECU,
+        /// and disposes the FTDI interface.
+        /// </summary>
+        void Disconnect();
+
         // ── Progress reporting ────────────────────────────────────────────────────
 
         /// <summary>
@@ -84,6 +110,22 @@ namespace HC_APTBS.Services
         /// </summary>
         string? DetectKLinePort();
 
+        // ── Mid-read notifications ────────────────────────────────────────────
+
+        /// <summary>
+        /// Raised during <see cref="ReadAllInfoAsync"/> as soon as the pump identifier
+        /// string has been read from ROM, before the full read completes.
+        /// Fires on a background thread; consumers must marshal to the UI thread.
+        /// </summary>
+        event Action<string>? PumpIdentified;
+
+        /// <summary>
+        /// Raised during <see cref="ReadAllInfoAsync"/> when the DFI calibration
+        /// value has been read from EEPROM. Parameter is the DFI angle in degrees.
+        /// Fires on a background thread; consumers must marshal to the UI thread.
+        /// </summary>
+        event Action<double>? DfiRead;
+
         // ── Power cycle callbacks ─────────────────────────────────────────────────
 
         /// <summary>