fix(windows): hide console when npm install helper spawns npm

Marketplace dependency install used spawn('npm') with a Windows shell but
without windowsHide, which flashes a console during npx claude-mem install.

src/npx-cli/install/npm-install-helper.ts

@@ -56,6 +56,7 @@ export function runNpmStrict(cwd: string, flags: string[]): Promise<NpmResult> {
     const child = spawn('npm', flags, {
       cwd,
       stdio: ['ignore', 'pipe', 'pipe'],
+      windowsHide: true,
       ...(IS_WINDOWS ? { shell: process.env.ComSpec ?? 'cmd.exe' } : {}),
     });
 

tests/npm-install-windows-hide.test.ts

@@ -0,0 +1,17 @@
+import { describe, it, expect } from 'bun:test';
+import { readFileSync } from 'fs';
+import { join } from 'path';
+
+const SOURCE = readFileSync(
+  join(import.meta.dir, '../src/npx-cli/install/npm-install-helper.ts'),
+  'utf8',
+);
+
+describe('npm-install-helper Windows spawn', () => {
+  it('hides the console window when spawning npm (incl. Windows shell)', () => {
+    expect(SOURCE).toContain('windowsHide: true');
+    expect(SOURCE).toMatch(
+      /spawn\(\s*'npm',\s*flags,\s*\{[\s\S]*?windowsHide:\s*true[\s\S]*?\}\)/,
+    );
+  });
+});