feat(theme-studio): explicit absolute-vs-relative face height kind

JSON collapses 2.0 to 2 on save, so a height's number type can't say whether it's a fixed 1/10pt value or a relative multiplier. The face model now carries an explicit heightMode field (abs/rel) through seed, save/load, and export. build-theme.el coerces :height from the kind: abs exports an integer, rel a float, so a relative 2.0 renders as 2.0, never 2.

Faces saved before the field existed infer the kind once on load (JS: integer to abs, fractional to rel; Python keeps the authored type, so a float 2.0 seed stays relative) and persist it on the next save. The mode-line seed carries abs explicitly, and WIP.json's eight seeded heights are stamped with their kinds. Regenerating the theme from the stamped WIP.json produces an identical WIP-theme.el, so the round-trip holds.

1 files changed, 13 insertions, 0 deletions

diff --git a/scripts/theme-studio/face_specs.py b/scripts/theme-studio/face_specs.py
index 1b3e150d..12eff16b 100644
--- a/scripts/theme-studio/face_specs.py
+++ b/scripts/theme-studio/face_specs.py
@@ -34,6 +34,7 @@ FACE_ATTRS: list[dict[str, Any]] = [
     {"model": "extend",     "default": False, "capture": ":extend",             "snapshot": "extend",            "kind": "bool"},
     {"model": "inherit",    "default": None,  "capture": ":inherit",            "snapshot": "inherit",           "kind": "scalar"},
     {"model": "height",     "default": None,  "capture": ":height",             "snapshot": "height",            "kind": "height"},
+    {"model": "heightMode", "default": None,  "capture": None,                  "snapshot": None,                "kind": None},
 ]
 
 # model key -> default, derived from the spec above (order preserved).
@@ -74,6 +75,18 @@ def migrate_legacy(spec: dict[str, Any]) -> dict[str, Any]:
             out["strike"] = {"color": None}
         elif strike is False:
             out["strike"] = None
+    # Height-kind migration: a spec saved before heightMode existed carries
+    # only the number, so infer the kind once -- int -> absolute 1/10pt,
+    # float -> relative multiplier. Unlike JS (where JSON collapses 2.0 to 2
+    # and only integrality is left to test), Python keeps the authored number
+    # type, so a float 2.0 seed correctly infers relative. An explicit
+    # heightMode always wins. The identity 1 and non-numbers infer nothing.
+    height = out.get("height")
+    if (out.get("heightMode") is None
+            and isinstance(height, (int, float))
+            and not isinstance(height, bool)
+            and height != 1):
+        out["heightMode"] = "abs" if isinstance(height, int) else "rel"
     return out