docs: bicorder_model.json is research-only (app integration removed in v1.3.0)

Verified: bicorder-app has no classifier implementation and reads
bicorder_model.json nowhere (src, build config); ascii_bicorder.py doesn't
use it either. Corrected the stale 'read by bicorder-app at build time'
claims in README, WORKFLOW, and the export script docstring.

analysis/scripts/export_model_for_js.py

@@ -1,6 +1,9 @@
 #!/usr/bin/env python3
 """
-Export the cluster classification model to JSON for use in JavaScript.
+Export the cluster classification model to JSON.
+
+Research-only export: the bicorder-app integration was removed in bicorder
+v1.3.0, so nothing in the app reads this model anymore.
 
 Reads dimension names directly from bicorder.json so the model always
 stays in sync with the current bicorder structure. Column renames and the