Add alignment state indicator and pluggable data sources

- AlignmentThresholds dataclass + VisionEngine.__init__ for injection
- alignment_state computed per snapshot (ready/aligning/fault)
- MonitorPlot circle/vector/legend driven by state color
- Status dot + label moved into POSITION VISUALIZATION panel header
- CsvSessionSource + DemoSource pluggable DataSource layer
- Synthetic DATA/ready/ and DATA/aligning/ sessions for visual testing
- Fix CAM 3 label placement (below circle, not above)

DATA/aligning/S20002P0.CSV

@@ -0,0 +1,53 @@
+# saved_on,SYNTHETIC
+# master_file,S20002P0.CSV
+# remote_begin,BEGIN_REMOTE_CSV SOURCE=LOCAL SPI=2 POINTS=49 MODE=SYNTHETIC STATUS=OK
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