Centralize formatter input hints

docs/prompt-architecture-improvement-plan.md

@@ -69,6 +69,8 @@ Formatter input/fallback parsing now has one home:
 It owns route-neutral parsing shared by Krea2, SDXL, and natural-caption
 routes:
 
+- input-hint choice lists and normalization for `auto`, `metadata_json`, and
+  route-specific text modes;
 - whitespace and punctuation normalization before formatter parsing;
 - JSON row detection from `metadata_json` or source text;
 - trigger-prefix stripping with route-specific trigger candidate lists;