feat: combine save/apply

resolves #45

src/lib/backup/compat/legacy-chords.ts

@@ -0,0 +1,21 @@
+import { KEYMAP_IDS } from "$lib/serial/keymap-codes"
+import type { CharaChordFile } from "$lib/share/chara-file"
+
+
+export function csvChordsToJson(csv: string): CharaChordFile {
+  return {
+    charaVersion: 1,
+    type: 'chords',
+    chords: csv.split('\n').map(line => {
+      const [input, output] = line.split(',', 2)
+      return [
+        input.split('+').map(it => KEYMAP_IDS.get(it.trim())?.code ?? 0),
+        output.split('').map(it => KEYMAP_IDS.get(it.trim())?.code ?? 0),
+      ]
+    })
+  }
+}
+
+export function isCsvLayout(csv: string): boolean {
+  return /^((\s*\w+\s*+?),\s*\w+\n?)+$/.test(csv)
+}