Add Canjector Start variant PCB layout

- Red solder mask PCB design
- Three variants now documented: Start, Middle, End

sources/2890/canjectors.md

@@ -50,10 +50,23 @@ The schematic shows the "middle" Canjector variant with:
 - **WAGO 2601 series** — tool-free, reliable terminal connections
 - **Designed in EasyEDA** — schematic dated 2026-04-09
 
+## Design Variants
+
+Chris designed three Canjector variants for different positions in the CAN bus topology:
+
+| Variant | Position | CAN Termination | Notes |
+|---------|----------|----------------|-------|
+| **Start** | Bus origin (PDH side) | No termination at this end | Upstream CAN connector from PDH |
+| **Middle** | Intermediate nodes | Switchable 120Ω | 3 CAN connections + 12V passthrough |
+| **End** | Bus terminus | Fixed 120Ω termination | Final node on the bus |
+
 ## Files
 
-- Schematic: `sources/2890/canjector-schematic.png`
-- CAD (if available): link to repo TBD
+| File | Description |
+|------|-------------|
+| `canjector-schematic.png` | Middle Canjector — EasyEDA schematic |
+| `canjector-start-pcb.png` | Start variant — PCB layout (red solder mask) |
+| `sources/2890/canjectors.md` | Full documentation |
 
 ## Connection to Training