feat(theme-studio): emit the full face-attribute model from build-theme

I extended build-theme's emitter to the full attribute set: family, distant-foreground, a weight and slant range, structured underline (color and wave), overline, strike color, inverse-video, extend, and inherit/height on every tier. It still reads the legacy boolean bold/italic/underline/strike fields, so every committed preset round-trips unchanged.

The emitter is the first piece of widening the studio to all face attributes; the model and UI that produce these fields come next. To keep the change clean I refactored --attrs from nine positional arguments to a single face-spec object and lifted the accessor helpers above their callers.

Added 40 ERT tests covering legacy compatibility, each new attribute, the coercion helpers' edge cases, and an end-to-end round-trip that loads a theme and reads the attributes back off the faces. They run in the theme-studio suite as a new stage.

1 files changed, 14 insertions, 0 deletions

diff --git a/scripts/theme-studio/run-tests.sh b/scripts/theme-studio/run-tests.sh
index 6666fb0b9..ab9c351ad 100755
--- a/scripts/theme-studio/run-tests.sh
+++ b/scripts/theme-studio/run-tests.sh
@@ -41,6 +41,20 @@ if node --test ./*.mjs >/tmp/ts-node.log 2>&1; then
   pass_msg "Node unit tests ($(grep -E '^. tests' /tmp/ts-node.log | grep -oE '[0-9]+' | head -1) tests)"
 else fail_msg "Node unit tests"; grep -E 'not ok|AssertionError|Error' /tmp/ts-node.log | sed 's/^/        /' | head -20; fi
 
+# 3b. ERT tests for build-theme.el (the theme.json -> deftheme emitter). The
+# tests live in the repo's tests/ dir; run them headless. Skip cleanly if no
+# emacs is on PATH (the JS/Python gates still run).
+BT_TESTS="$HERE/../../tests/test-build-theme.el"
+if command -v emacs >/dev/null 2>&1 && [ -f "$BT_TESTS" ]; then
+  if emacs --batch --no-site-file --no-site-lisp \
+       -L "$HERE/../.." -L "$HERE/../../modules" -L "$HERE/../../tests" -L "$HERE/../../themes" \
+       -l "$BT_TESTS" -f ert-run-tests-batch-and-exit >/tmp/ts-bt.log 2>&1; then
+    pass_msg "build-theme.el ERT tests ($(grep -oE 'Ran [0-9]+' /tmp/ts-bt.log | awk '{print $2}') tests)"
+  else fail_msg "build-theme.el ERT tests"; grep -E 'FAILED|Error' /tmp/ts-bt.log | sed 's/^/        /' | head -20; fi
+else
+  skip_msg "build-theme.el ERT tests (no emacs on PATH)"
+fi
+
 # 4. Syntax-check the inlined page script.
 python3 - <<'PY' && node --check /tmp/ts-script.js >/dev/null 2>&1 && pass_msg "spliced page <script> parses" || fail_msg "spliced page <script> syntax"
 import re