feat(ext/shared): glyph constants module for unified icon language

Centralizes the unicode glyphs used by sidebar nav and form action buttons
so popup and fullscreen surfaces stay in sync. Includes the REQUIRED_PILL
snippet used to replace the trailing-asterisk required-field marker.

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

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

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

@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest';
+import * as glyphs from '../glyphs';
+
+describe('glyphs', () => {
+  it('exports the documented glyph constants', () => {
+    expect(glyphs.GLYPH_REVEAL).toBe('⊙');
+    expect(glyphs.GLYPH_HIDE).toBe('⊘');
+    expect(glyphs.GLYPH_GENERATE).toBe('↻');
+    expect(glyphs.GLYPH_FILL_FROM_TAB).toBe('⤓');
+    expect(glyphs.GLYPH_QR).toBe('◫');
+    expect(glyphs.GLYPH_MONO).toBe('≡');
+    expect(glyphs.GLYPH_TRASH).toBe('▦');
+    expect(glyphs.GLYPH_DEVICES).toBe('⌬');
+    expect(glyphs.GLYPH_SETTINGS).toBe('⚙');
+    expect(glyphs.GLYPH_LOCK).toBe('⏻');
+  });
+
+  it('exports REQUIRED_PILL as an HTML snippet', () => {
+    expect(glyphs.REQUIRED_PILL).toBe('<span class="req-pill">required</span>');
+  });
+});