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>

.claude/skills/protocol-ref/SKILL.md

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+# VP44 Protocol Reference
+
+Quick reference for hardware protocol constants used in HC_APTBS. Consult this before modifying any protocol-related code.
+
+---
+
+## DFI encoding (EEPROM address 0x0044 on VP44 ECU)
+
+**Read (raw byte → DFI value):**
+```csharp
+dfi = (sbyte)raw * 3.0 / 256.0
+```
+
+**Write (DFI value → raw byte):**
+```csharp
+raw = (sbyte)((dfi * 256.0f) / 3.0f)
+// If raw == 0, use 1 — the ECU rejects zero
+```
+
+**Checksum:**
+```csharp
+checksum = (byte)(0 - (byte)rawValue)
+```
+
+---
+
+## IIR low-pass filter (PcanAdapter.PassFilterUpdate)
+
+```csharp
+result = Math.Round(prev + alpha * (value - prev), 4)
+```
+
+Used to smooth CAN bus sensor readings. The `alpha` coefficient controls responsiveness vs. noise rejection.
+
+---
+
+## OEM legitimation (PcanAdapter.Connect)
+
+```csharp
+token = (20120378UL << 32) | 21200UL
+```
+
+Sent as a CAN frame to authenticate with the bench controller. Without this, the bench ignores all commands.
+
+---
+
+## K-Line / KWP timing
+
+**Inter-byte delay** (`KW1281Connection.SendPacket`):
+```csharp
+Thread.Sleep(5)  // after each byte — KWP protocol requirement, NOT a workaround
+```
+
+**5-baud slow-init** (`KwpCommon.WakeUp`):
+- Bit-bangs the ECU address at 5 baud on the K-Line
+- Sleep durations in WakeUp are protocol-mandated — do not change
+
+**Session lifetime**:
+- One `FtdiInterface` open/close per KWP operation
+- ECU expects a fresh session per dialog — do not pool connections
+
+---
+
+## CAN bus (PCAN-Basic, 500 kbps)
+
+- Channel: `PCAN_USBBUS1`
+- Baud: `PCAN_BAUD_500K`
+- Read thread polls with `Thread.Sleep(2)` in `DrainMessageQueue` (known debt)
+
+---
+
+## Caution
+
+Do not change any of these values without understanding the hardware protocol specification. Incorrect values can cause ECU communication failures or bench malfunction.