feat(theme-studio): nerd-icons gallery as a hue-ordered icon grid

The nerd-icons pane is now a grid: one row per color face, the rows ordered by hue so families cluster, distinct icons (deduped within a color) drawn in their color with the icon's nerd-font name beneath. A "preview:" dropdown above the grid picks the glyph size in points, with Left/Right arrows to step it. Single-pane apps show it disabled, naming the preview. This replaces the v1 legend in the pane, whose data is still captured for round-trip.

build-nerd-icons-legend.el is now a library. A cj/nerd-icons-write-legend entry point requires nerd-icons only at write time, so the capture logic loads and unit-tests without it. It dedupes icons by name within a face, computes each face's native hue, and orders the groups by hue. Writing the test surfaced a latent bug: face-hsl used (cadr (assoc t spec)), which grabs the first keyword instead of the plist. It only worked because the real faces fall through to the face-foreground branch. I fixed it to a correct t-clause parse.

Coverage: 7 ERT capture tests (dedupe, hue order, lightness tiebreak, name sort, skip rules), 4 Python validator edges, and browser gates for the grid and the size dropdown.

Locate stays color-level: clicking a color flashes its icons, and clicking an icon flashes its color row. Icons aren't individually editable, so there's nothing per-icon to select.

1 files changed, 2 insertions, 1 deletions

diff --git a/scripts/theme-studio/run-tests.sh b/scripts/theme-studio/run-tests.sh
index 6107287d7..f2daa74b5 100755
--- a/scripts/theme-studio/run-tests.sh
+++ b/scripts/theme-studio/run-tests.sh
@@ -47,10 +47,11 @@ else fail_msg "Node unit tests"; grep -E 'not ok|AssertionError|Error' /tmp/ts-n
 # headless batch. Skip cleanly if no emacs is on PATH (JS/Python gates still run).
 BT_TESTS="$HERE/../../tests/test-build-theme.el"
 FD_TESTS="$HERE/test-face-docs-dump.el"
+NL_TESTS="$HERE/test-nerd-icons-legend-dump.el"
 if command -v emacs >/dev/null 2>&1 && [ -f "$BT_TESTS" ]; then
   if emacs --batch --no-site-file --no-site-lisp \
        -L "$HERE/../.." -L "$HERE/../../modules" -L "$HERE/../../tests" -L "$HERE/../../themes" \
-       -l "$BT_TESTS" -l "$FD_TESTS" -f ert-run-tests-batch-and-exit >/tmp/ts-bt.log 2>&1; then
+       -l "$BT_TESTS" -l "$FD_TESTS" -l "$NL_TESTS" -f ert-run-tests-batch-and-exit >/tmp/ts-bt.log 2>&1; then
     pass_msg "theme-studio ERT tests ($(grep -oE 'Ran [0-9]+' /tmp/ts-bt.log | awk '{print $2}') tests)"
   else fail_msg "theme-studio ERT tests"; grep -E 'FAILED|Error' /tmp/ts-bt.log | sed 's/^/        /' | head -20; fi
 else