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, 43 insertions, 10 deletions

diff --git a/scripts/theme-studio/face_specs.py b/scripts/theme-studio/face_specs.py
index 697eec50f..5fa038068 100644
--- a/scripts/theme-studio/face_specs.py
+++ b/scripts/theme-studio/face_specs.py
@@ -5,20 +5,20 @@ from __future__ import annotations
 from typing import Any
 
 
-# The full per-face attribute model. inherit and height live here (every tier
-# can set them now, not just packages). bold/italic/underline/strike stay as the
-# legacy booleans for this phase; the weight/slant/underline-object cutover lands
-# with the editor widgets that force it. distant-fg, family, overline, inverse,
-# and extend are added in their final shape (no legacy form to migrate).
+# The full per-face attribute model, in its final shape. weight and slant replace
+# the legacy bold/italic booleans (weight is one of light/normal/medium/semibold/
+# bold/heavy; slant is normal/italic/oblique). underline and strike are objects:
+# underline is {style: line|wave, color} and strike is {color}; null means unset.
+# inherit and height are no longer package-only — every tier can set them.
 STYLE_DEFAULTS: dict[str, Any] = {
     "fg": None,
     "bg": None,
     "distant-fg": None,
     "family": None,
-    "bold": False,
-    "italic": False,
-    "underline": False,
-    "strike": False,
+    "weight": None,
+    "slant": None,
+    "underline": None,
+    "strike": None,
     "overline": None,
     "box": None,
     "inverse": False,
@@ -32,10 +32,43 @@ STYLE_DEFAULTS: dict[str, Any] = {
 PACKAGE_DEFAULTS: dict[str, Any] = dict(STYLE_DEFAULTS)
 
 
+def migrate_legacy(spec: dict[str, Any]) -> dict[str, Any]:
+    """Convert a face spec's legacy boolean style fields to the new shape.
+
+    bold -> weight "bold", italic -> slant "italic", underline true ->
+    {style: line, color: null}, strike true -> {color: null}. An explicit
+    weight/slant already present wins over the legacy flag. Specs already in the
+    new shape pass through unchanged, so this is safe to apply to any input. The
+    JS side mirrors this in app-core.js migrateLegacyFace; keep them in step.
+    """
+    out = dict(spec)
+    if "bold" in out:
+        bold = out.pop("bold")
+        if bold and not out.get("weight"):
+            out["weight"] = "bold"
+    if "italic" in out:
+        italic = out.pop("italic")
+        if italic and not out.get("slant"):
+            out["slant"] = "italic"
+    if "underline" in out:
+        underline = out["underline"]
+        if underline is True:
+            out["underline"] = {"style": "line", "color": None}
+        elif underline is False:
+            out["underline"] = None
+    if "strike" in out:
+        strike = out["strike"]
+        if strike is True:
+            out["strike"] = {"color": None}
+        elif strike is False:
+            out["strike"] = None
+    return out
+
+
 def face_spec(spec: dict[str, Any] | None = None, *, package: bool = False) -> dict[str, Any]:
     out = dict(PACKAGE_DEFAULTS if package else STYLE_DEFAULTS)
     if spec:
-        out.update(spec)
+        out.update(migrate_legacy(spec))
     return out