feat(ext/shared): add colorizePassword utility

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

extension/src/shared/__tests__/password-coloring.test.ts

@@ -0,0 +1,60 @@
+import { describe, it, expect } from 'vitest';
+import { colorizePassword, PWD_DIGIT, PWD_SYMBOL, PWD_LETTER } from '../password-coloring';
+
+describe('colorizePassword', () => {
+
+  function classes(frag: DocumentFragment): string[] {
+    return Array.from(frag.querySelectorAll('span')).map(s => s.className);
+  }
+  function texts(frag: DocumentFragment): string[] {
+    return Array.from(frag.querySelectorAll('span')).map(s => s.textContent ?? '');
+  }
+
+  it('returns empty fragment for empty input', () => {
+    const frag = colorizePassword('');
+    expect(frag.childNodes.length).toBe(0);
+  });
+
+  it('classifies a mixed-class run', () => {
+    const frag = colorizePassword('aB3$xY');
+    expect(classes(frag)).toEqual([PWD_LETTER, PWD_DIGIT, PWD_SYMBOL, PWD_LETTER]);
+    expect(texts(frag)).toEqual(['aB', '3', '$', 'xY']);
+  });
+
+  it('all-letters produces a single letter span', () => {
+    const frag = colorizePassword('passwd');
+    expect(classes(frag)).toEqual([PWD_LETTER]);
+    expect(texts(frag)).toEqual(['passwd']);
+  });
+
+  it('all-digits produces a single digit span', () => {
+    const frag = colorizePassword('123456');
+    expect(classes(frag)).toEqual([PWD_DIGIT]);
+    expect(texts(frag)).toEqual(['123456']);
+  });
+
+  it('all-symbols produces a single symbol span', () => {
+    const frag = colorizePassword('!@#$%^');
+    expect(classes(frag)).toEqual([PWD_SYMBOL]);
+    expect(texts(frag)).toEqual(['!@#$%^']);
+  });
+
+  it('classifies unicode letters as letters', () => {
+    const frag = colorizePassword('áñü');
+    expect(classes(frag)).toEqual([PWD_LETTER]);
+  });
+
+  it('classifies whitespace as symbol', () => {
+    const frag = colorizePassword('a b');
+    expect(classes(frag)).toEqual([PWD_LETTER, PWD_SYMBOL, PWD_LETTER]);
+    expect(texts(frag)).toEqual(['a', ' ', 'b']);
+  });
+
+  it('representative password snapshot: aB3$xY7&_!', () => {
+    const frag = colorizePassword('aB3$xY7&_!');
+    expect(classes(frag)).toEqual([
+      PWD_LETTER, PWD_DIGIT, PWD_SYMBOL, PWD_LETTER, PWD_DIGIT, PWD_SYMBOL,
+    ]);
+    expect(texts(frag)).toEqual(['aB', '3', '$', 'xY', '7', '&_!']);
+  });
+});