feat: create skill variable helper

modules/home/programs/terminal/pi/config/skills/create-skill/assets/variable.sh

@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+# Skill-local variable store. Values live in <skill-dir>/.vars/<NAME>.
+#
+# Usage:
+#   variable.sh --get NAME           # prints value to stdout, exits 0
+#                                    # or prints a self-explaining hint to
+#                                    # stderr and exits 2 if unset.
+#   variable.sh --set NAME VALUE     # writes value, exits 0.
+#
+# Callers should treat a non-zero exit as fatal; the stderr message tells
+# the caller (agent or user) exactly how to populate the missing value.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SKILL_DIR="$(dirname "$SCRIPT_DIR")"
+STORE="$SKILL_DIR/.vars"
+SELF="$0"
+
+usage() {
+    cat >&2 <<EOF
+Usage:
+  $SELF --get NAME
+  $SELF --set NAME VALUE
+EOF
+    exit 2
+}
+
+case "${1:-}" in
+    --get)
+        [[ $# -eq 2 ]] || usage
+        name="$2"
+        file="$STORE/$name"
+        if [[ ! -f "$file" ]]; then
+            cat >&2 <<EOF
+$SELF: $name is not set.
+Ask the user for the value, then set it:
+  $SELF --set $name <value>
+EOF
+            exit 2
+        fi
+        cat "$file"
+        ;;
+    --set)
+        [[ $# -eq 3 ]] || usage
+        name="$2"; value="$3"
+        [[ "$name" =~ ^[A-Z][A-Z0-9_]*$ ]] || {
+            echo >&2 "$SELF: invalid name '$name' (must match [A-Z][A-Z0-9_]*)"
+            exit 2
+        }
+        mkdir -p "$STORE"
+        # Self-ignore the store so values never get committed, even if the
+        # skill root lacks a .gitignore entry for .vars/.
+        [[ -f "$STORE/.gitignore" ]] || printf '*\n' > "$STORE/.gitignore"
+        printf '%s' "$value" > "$STORE/$name"
+        ;;
+    *)
+        usage
+        ;;
+esac