docs(developer): document the vision pipeline architecture

Generic reference for VisionInterface/SampleVisionMonitor (the three-layer
camera-processing architecture, ROI cropping, position-blind shape scoring
vs. position_tolerance_px, and reading diagnostic_image), plus the
device_manager-injection pitfall for any future PSIDeviceBase subclass that
needs to resolve sibling devices -- written up the same way as the existing
lamni_smear_architecture.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C9zgK28uPoZWJFkJWV4P1G

docs/developer/developer.md

@@ -10,6 +10,7 @@ hidden: true
 
 editing_docs
 lamni_smear_architecture
+vision_pipeline_architecture
 
 ```
 
@@ -42,4 +43,15 @@ Conventions for writing these MyST/Sphinx docs and how changes go live on Read t
 Device/ipython-client/GUI widget interfaces for the smear rotation-center calibration aid, and the `bw-generate-cli` regeneration pitfall.
 ```
 
+```{grid-item-card}
+:link: developer.vision_pipeline
+:link-type: ref
+:text-align: center
+:class-item: index-card
+
+## Vision pipeline architecture
+
+The generic `VisionInterface`/`SampleVisionMonitor` camera-processing layer, the `PreviewSignal` rpc_access gotcha, and the `device_manager` injection pitfall.
+```
+
 ````