feat(ext): add GLYPH_NEXT and replace ASCII arrows with ▸

Replaces the ASCII rightwards arrow → with U+25B8 ▸ in settings-vault
buttons. Matches the existing ▾/▸ disclosure-glyph family.

extension/src/shared/__tests__/glyphs.test.ts

@@ -1,5 +1,10 @@
 import { describe, it, expect } from 'vitest';
 import * as glyphs from '../glyphs';
+import {
+  GLYPH_REVEAL, GLYPH_HIDE, GLYPH_GENERATE, GLYPH_FILL_FROM_TAB,
+  GLYPH_QR, GLYPH_MONO, GLYPH_TRASH, GLYPH_DEVICES, GLYPH_SETTINGS,
+  GLYPH_LOCK, GLYPH_NEXT,
+} from '../glyphs';
 
 describe('glyphs', () => {
   it('exports the documented glyph constants', () => {
@@ -19,3 +24,20 @@ describe('glyphs', () => {
     expect(glyphs.REQUIRED_PILL_HTML).toBe('<span class="req-pill">required</span>');
   });
 });
+
+describe('glyph constants', () => {
+  it('uses single unicode codepoints (no emoji multi-codepoint)', () => {
+    const all = [
+      GLYPH_REVEAL, GLYPH_HIDE, GLYPH_GENERATE, GLYPH_FILL_FROM_TAB,
+      GLYPH_QR, GLYPH_MONO, GLYPH_TRASH, GLYPH_DEVICES, GLYPH_SETTINGS,
+      GLYPH_LOCK, GLYPH_NEXT,
+    ];
+    for (const g of all) {
+      expect([...g].length).toBe(1);
+    }
+  });
+
+  it('GLYPH_NEXT is the small right triangle (U+25B8)', () => {
+    expect(GLYPH_NEXT).toBe('▸');
+  });
+});