Subaru D | Additional Passthrough Pins Needed for More Support

Based on my & other folks' findings, we can support more cars on the existing Subaru D Harness by only adding more passthrough pins.

* 2021 Outback (AU) - requires a passthrough on pin 6. #18
* 2026 Crosstrek - Existing D (Same for ICE / Hybrid)
* 2026 Impreza - Existing D
* 2026 Ascent - Existing D
* 2026 WRX - Existing D (Actually is missing 2 pins that are passthrough on normal D)
* 2026 Forester - requires passthrough on pin 3 and pin 15 for EYE local 1 CAN L and EYE local 1 CAN H respectively. I do not have a Forester to test on, but the existing D connecter is passthrough on EYE local 2 CAN L and EYE local 2 CAN H (Same for ICE / Hybrid)
* 2026 Outback - quite a few more wires. we will need passthrough on at least pin 3 ((K)_Rear advanced
safety CAN L), pin 6 (LIN communication), and pin 15 ((K)_Rear advanced
safety CAN H)

All-in, adding passthroughs on pins 3, 6, and 15 should be all that is needed

[2026BRZEyesightSecurityGateway.pdf](https://github.com/user-attachments/files/25855514/2026BRZEyesightSecurityGateway.pdf)
[2026BRZEyesight.pdf](https://github.com/user-attachments/files/25855507/2026BRZEyesight.pdf)
[2026AscentEyesight.pdf](https://github.com/user-attachments/files/25855515/2026AscentEyesight.pdf)
[2026OutbackEyesight.pdf](https://github.com/user-attachments/files/25855511/2026OutbackEyesight.pdf)
[2025CrosstrekImprezaICEEyesight.pdf](https://github.com/user-attachments/files/25855509/2025CrosstrekImprezaICEEyesight.pdf)
[2026ForesterHybridEyesight.pdf](https://github.com/user-attachments/files/25855513/2026ForesterHybridEyesight.pdf)
[2026CrosstrekImprezaHybridEyesight.pdf](https://github.com/user-attachments/files/25855516/2026CrosstrekImprezaHybridEyesight.pdf)
[2026WRXEyesight.pdf](https://github.com/user-attachments/files/25855512/2026WRXEyesight.pdf)
[2026ForesterICEEyesight.pdf](https://github.com/user-attachments/files/25855510/2026ForesterICEEyesight.pdf)
[2026CrosstrekImprezaICEEyesight.pdf](https://github.com/user-attachments/files/25855508/2026CrosstrekImprezaICEEyesight.pdf)

Start by reviewing the attached Subaru Eyesight PDFs, especially the 2026 Forester, Outback, WRX, Crosstrek, Impreza, and Ascent documents, and compare their connector pin requirements with the existing Subaru D harness. Done means confirming the required passthrough pins and updating the harness design to support pins 3, 6, and 15 without breaking existing vehicle compatibility.

Written by the indexing model from the issue text.