feat: add platform detection script

scripts/detect_platform.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# detect_platform.sh — Print the Inkscape config root for this system.
+# Usage: source scripts/detect_platform.sh && echo "$INKSCAPE_CONFIG"
+# Sets: INKSCAPE_CONFIG (path), INKSCAPE_INSTALL_METHOD (flatpak|snap|native)
+
+set -euo pipefail
+
+_detect_inkscape_config() {
+    # Flatpak takes priority — most common modern Linux install
+    local flatpak_config="$HOME/.var/app/org.inkscape.Inkscape/config/inkscape"
+    if [[ -d "$flatpak_config" ]] || flatpak list 2>/dev/null | grep -q "org.inkscape.Inkscape"; then
+        INKSCAPE_CONFIG="$flatpak_config"
+        INKSCAPE_INSTALL_METHOD="flatpak"
+        return 0
+    fi
+
+    # Snap
+    local snap_config="$HOME/snap/inkscape/current/.config/inkscape"
+    if [[ -d "$snap_config" ]] || snap list 2>/dev/null | grep -q "^inkscape "; then
+        INKSCAPE_CONFIG="$snap_config"
+        INKSCAPE_INSTALL_METHOD="snap"
+        return 0
+    fi
+
+    # Native / XDG
+    local xdg_config="${XDG_CONFIG_HOME:-$HOME/.config}/inkscape"
+    INKSCAPE_CONFIG="$xdg_config"
+    INKSCAPE_INSTALL_METHOD="native"
+    return 0
+}
+
+_detect_inkscape_config