style(ext/vault): replace sidebar emoji nav with monochrome glyphs

▦ trash · ⌬ devices · ⚙ settings · ⏻ lock — all imported from the new
shared/glyphs module so popup and fullscreen stay in sync. Regression
test scans the source for the old escape-coded emoji to prevent
backsliding.

Plan 2026-04-30 fullscreen UX phase 1 task 5.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

extension/src/vault/__tests__/sidebar-glyphs.test.ts

@@ -0,0 +1,29 @@
+import { describe, it, expect } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+
+describe('vault sidebar glyphs', () => {
+  const vaultSrc = fs.readFileSync(
+    path.resolve(__dirname, '../vault.ts'),
+    'utf-8',
+  );
+
+  it('uses GLYPH_TRASH instead of the trash emoji', () => {
+    expect(vaultSrc).not.toMatch(/\u{1F5D1}/u);
+    expect(vaultSrc).toContain('GLYPH_TRASH');
+  });
+
+  it('uses GLYPH_DEVICES instead of the devices emoji', () => {
+    expect(vaultSrc).not.toMatch(/\u{1F4F1}/u);
+    expect(vaultSrc).toContain('GLYPH_DEVICES');
+  });
+
+  it('uses GLYPH_LOCK instead of the lock emoji', () => {
+    expect(vaultSrc).not.toMatch(/\u{1F512}/u);
+    expect(vaultSrc).toContain('GLYPH_LOCK');
+  });
+
+  it('uses GLYPH_SETTINGS for the settings nav', () => {
+    expect(vaultSrc).toContain('GLYPH_SETTINGS');
+  });
+});