Centralize formatter route metadata

docs/prompt-architecture-improvement-plan.md

@@ -188,6 +188,10 @@ Already isolated:
   rows now emit `action_family`, `position_family`, `position_key`, and
   `position_keys` so formatter routing and debugging do less keyword guessing.
   Krea, SDXL, and training-caption routes consume these fields when present.
+- shared row route metadata readers live in `route_metadata.py`, covering
+  normalized action family, position family/keys, and route-specific formatter
+  hints for Krea, SDXL, and training-caption routes. Position keys are strict
+  by default, while SDXL can opt into legacy unknown key tags for compatibility.
 - final row and pair text normalization lives in `row_normalization.py`,
   covering trigger prepending, extra-positive append, negative merge/dedupe,
   caption-part joining, and embedded soft/hard row sanitation before metadata
@@ -270,12 +274,14 @@ Already isolated:
   stripping, the shared prompt field-label inventory, prompt-field extraction,
   `Avoid:` splitting, and row-value fallback for Krea, SDXL, and caption
   routes.
+- `route_metadata.py` owns shared row-level action-family, position-family,
+  position-key, and formatter-hint reads so formatter routes do not normalize
+  these fields independently.
 
 Improve later:
 
-- extend SDXL and caption routes to optionally consume `action_family` /
-  `position_family` when ordering tags or caption clauses;
-- add route-level smoke fixtures for representative metadata rows;
+- keep adding route-level smoke fixtures when new metadata fields start
+  influencing formatter output;
 
 ### SDXL Formatter Path
 
@@ -290,6 +296,7 @@ Keep here:
 - negative-prompt assembly.
 - metadata-family tag hints from `action_family`, `position_family`, and
   `position_keys`.
+- shared row route metadata reads from `route_metadata.py`.
 - shared formatter input parsing from `formatter_input.py`.
 - style presets, quality presets, default negative prompt, and action/position
   family tag hints from `sdxl_presets.py`.
@@ -313,6 +320,7 @@ Keep here:
 - style-tail policy from `caption_policy.py`.
 - metadata-family action labels from `action_family` and `position_family` via
   `caption_policy.py`.
+- shared row route metadata reads from `route_metadata.py`.
 - shared formatter input parsing from `formatter_input.py`.
 - shared cast descriptor parsing and label replacement from `krea_cast.py`.
 - caption detail-level/style-policy normalization, clothing cleanup, and