refactor(theme-studio): cut the face model over to weight/slant/objects

I replaced the legacy bold/italic/underline/strike booleans with the final model shape across both sides of the tool. weight (light/normal/medium/semibold/bold/heavy) and slant (normal/italic/oblique) replace the bold/italic flags, underline becomes {style: line|wave, color}, strike becomes {color}, and null means unset.

A single migration converts a legacy face on the way in, mirrored as migrateLegacyFace in app-core.js and migrate_legacy in face_specs.py so the JS and Python models can't drift. It runs on import (applyImported, mergePackagesInto) and on every seed that face_spec touches. The captured-snapshot seed (default_faces.seed) narrows the same way it did before. Only bold and italic survive, as weight "bold" and slant "italic", so the generated themes stay byte-identical.

The B/I/U/S toggle buttons keep working through a transitional bridge (legacyStyleOn / toggleLegacyStyle). The weight/slant dropdowns and underline/strike controls that replace them land next. The live previews read the new shape, with a weight name mapped to a numeric CSS font-weight.

The cutover is proven emit-neutral two ways. An ERT test asserts the migrated shapes emit the same attributes as the legacy booleans, and deep-migrating every face in dupre, distinguished, sterling, now, theme, and WIP then running build-theme yields byte-identical output. Full suite green: Python 59, Node 200, ERT 41, plus the browser hash gates.

1 files changed, 9 insertions, 4 deletions

diff --git a/scripts/theme-studio/default_faces.py b/scripts/theme-studio/default_faces.py
index ce2bf3196..c8f7167d1 100644
--- a/scripts/theme-studio/default_faces.py
+++ b/scripts/theme-studio/default_faces.py
@@ -44,14 +44,19 @@ class DefaultFaces:
             out["fg"] = fg
         if bg:
             out["bg"] = bg
+        # Representation-only cutover: the snapshot's bold/italic become the new
+        # weight/slant shape, and underline/strike become objects. The same
+        # narrowing as before (only "bold"/"italic" survive; richer weights and
+        # underline colors wait for the snapshot refresh), so the emitted theme
+        # is byte-identical.
         if data.get("weight") == "bold":
-            out["bold"] = True
+            out["weight"] = "bold"
         if data.get("slant") == "italic":
-            out["italic"] = True
+            out["slant"] = "italic"
         if data.get("underline"):
-            out["underline"] = True
+            out["underline"] = {"style": "line", "color": None}
         if data.get("strike"):
-            out["strike"] = True
+            out["strike"] = {"color": None}
         if data.get("inherit"):
             out["inherit"] = data.get("inherit")
         if data.get("height") and data.get("height") != 1: