feat(editor): eslint/tsconfig migration + type fixes

@robonen/editor: migrate to eslint flat config + composite tsconfig; fix
convergence test type annotations.

vue/editor/src/keymap/compile.ts

@@ -0,0 +1,22 @@
+import type { Command } from '../state';
+import type { Platform } from '../view/config';
+import type { Keymap } from './types';
+import { normalizeCombo } from './normalize';
+
+/**
+ * Merge ordered keymaps into a single normalized lookup. Earlier keymaps win, so
+ * pass user overrides before the defaults: `compileKeymaps([user, defaults], …)`.
+ */
+export function compileKeymaps(keymaps: readonly Keymap[], platform: Platform): Map<string, Command> {
+  const compiled = new Map<string, Command>();
+
+  for (const keymap of keymaps) {
+    for (const combo in keymap) {
+      const normalized = normalizeCombo(combo, platform);
+      if (!compiled.has(normalized))
+        compiled.set(normalized, keymap[combo]!);
+    }
+  }
+
+  return compiled;
+}