docs: update CHANGELOG to mention manual_painted column in CSV export

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Author: patcon

CHANGELOG.md

@@ -4,7 +4,7 @@
 
 ### Added
 
-- "Download Data" button in the projection selector panel to export participant metadata as `participants.csv` ([#33](https://github.com/patcon/polislike-human-cartography-prototype-v2/issues/33)). A confirmation dialog shows participant and column counts before downloading.
+- "Download Data" button in the projection selector panel to export participant metadata as `participants.csv` ([#33](https://github.com/patcon/polislike-human-cartography-prototype-v2/issues/33)). A confirmation dialog shows participant and column counts before downloading. Includes a `manual_painted` column reflecting any painted group assignments (blank if unpainted).
 - `FloatingModal` legend when viewing an obs-column annotation in the metrics layer ([#29](https://github.com/patcon/polislike-human-cartography-prototype-v2/issues/29)).
   - Shows the column name as the label and colored category swatches for categorical columns; continuous columns show an empty modal (legend to follow).
   - Prev/next arrows (and ←/→ keyboard shortcuts) cycle through available obs columns, updating the active annotation.