fix(scripts): make install.sh / build.sh work on stock macOS

Stock macOS ships bash 3.2 (frozen 2007 due to GPLv3) and BSD find.
Both scripts used `mapfile` (bash 4+) and `find -printf` (GNU only),
so a fresh Mac user running `bash scripts/install.sh` died on line 11
before copying anything. Replace with a portable shell glob — same
sort order, no `find` dependency, works on bash 3.2 and 4+.

Verified on git-bash: 16 skills discovered, install dry-run copies all,
`build.sh` produces a valid archive.

See .wiki/concepts/install-portability.md for the full gotcha.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/build.sh

@@ -15,7 +15,15 @@ DIST="$ROOT/dist"
 if command -v zip >/dev/null 2>&1; then
   mkdir -p "$DIST"
   if [ "$#" -eq 0 ]; then
-    mapfile -t names < <(find "$SRC" -mindepth 1 -maxdepth 1 -type d -printf '%f\n' | sort)
+    # Portable across bash 3.2 (stock macOS) and bash 4+ (Linux, git-bash):
+    # avoid `mapfile` (bash 4+) and `find -printf` (GNU find only).
+    names=()
+    for d in "$SRC"/*/; do
+      [ -d "$d" ] || continue
+      names+=("$(basename "$d")")
+    done
+    IFS=$'\n' names=($(printf '%s\n' "${names[@]}" | sort))
+    unset IFS
   else
     names=("$@")
   fi

scripts/install.sh

@@ -8,7 +8,15 @@ SRC="$ROOT/skills"
 TARGET="${CLAUDE_SKILLS_DIR:-$HOME/.claude/skills}"
 
 if [ "$#" -eq 0 ]; then
-  mapfile -t names < <(find "$SRC" -mindepth 1 -maxdepth 1 -type d -printf '%f\n' | sort)
+  # Portable across bash 3.2 (stock macOS) and bash 4+ (Linux, git-bash):
+  # avoid `mapfile` (bash 4+) and `find -printf` (GNU find only).
+  names=()
+  for d in "$SRC"/*/; do
+    [ -d "$d" ] || continue
+    names+=("$(basename "$d")")
+  done
+  IFS=$'\n' names=($(printf '%s\n' "${names[@]}" | sort))
+  unset IFS
 else
   names=("$@")
 fi