refactor(main): split main.ts into focused runtime modules (#123)

src/main/password-store-args.test.ts

@@ -0,0 +1,7 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { getPasswordStoreArg } from './password-store-args';
+
+test('getPasswordStoreArg ignores split-form whitespace-only values', () => {
+  assert.equal(getPasswordStoreArg(['SubMiner.AppImage', '--password-store', '   ']), null);
+});