feat(statusbar): word count + reading time + Flesch-Kincaid grade

- src/utils/writing-stats.js — pure module: stripMarkdown() drops fenced
  code blocks, inline code, image URLs, link URLs, headings, blockquote
  markers, list bullets, and emphasis markers so the word count reflects
  the prose a reader actually consumes (the convention used by Hemingway,
  iA Writer). splitSentences / countSyllables use Flesch's standard
  heuristics. computeStats returns wordCount, sentenceCount,
  syllableCount, readingTimeMinutes (default 220 wpm),
  fleschKincaidGrade, charCount.
- src/renderer.js — _updateStatusBar now calls computeStats and updates
  three new status items: ~X min read, Grade N.N, and the existing Words
  + Chars counters use the stripped count.
- src/index.html — two new status items: #reading-time and #grade-level.

Tests (23 new, tests/writing-stats.test.js): markdown stripping (fenced,
inline, images, links, wikilinks, headings, lists, emphasis, HTML),
sentence splitter edge cases, syllable heuristic (short words, silent e,
empty), and computeStats with custom wpm + null-safe inputs.

Full suite: 68 suites, 789 tests, lint+format clean.

Amit Haridas

tests/writing-stats.test.js

@@ -0,0 +1,180 @@
+/**
+ * @jest-environment node
+ *
+ * writing-stats tests — pure module, no IO.
+ */
+const {
+  stripMarkdown,
+  splitSentences,
+  countSyllablesInWord,
+  countSyllables,
+  countWords,
+  computeStats,
+} = require('../src/utils/writing-stats');
+
+describe('stripMarkdown', () => {
+  test('removes fenced code blocks', () => {
+    expect(stripMarkdown('hello\n```js\nfoo();\n```\nworld')).toMatch(/hello/);
+    expect(stripMarkdown('hello\n```js\nfoo();\n```\nworld')).not.toMatch(/foo/);
+  });
+
+  test('removes inline code', () => {
+    expect(stripMarkdown('use the `npm install` command')).not.toMatch(/npm install/);
+    expect(stripMarkdown('use the `npm install` command')).toMatch(/use the/);
+  });
+
+  test('strips image syntax entirely (URLs are not prose)', () => {
+    expect(stripMarkdown('see ![diagram](https://x.com/a.png) here')).not.toMatch(/x\.com/);
+    expect(stripMarkdown('see ![diagram](https://x.com/a.png) here')).toMatch(/see/);
+  });
+
+  test('keeps link text but drops URLs', () => {
+    expect(stripMarkdown('read [the docs](https://docs.example.com) now')).toMatch(/the docs/);
+    expect(stripMarkdown('read [the docs](https://docs.example.com) now')).not.toMatch(/docs\.example/);
+  });
+
+  test('keeps wikilink visible labels', () => {
+    expect(stripMarkdown('see [[Project X|the project]] page')).toMatch(/the project/);
+  });
+
+  test('strips heading hashes, blockquote markers, list bullets', () => {
+    expect(stripMarkdown('# Title\n\n> A quote\n\n- a bullet\n\n1. numbered')).toMatch(/Title/);
+    expect(stripMarkdown('# Title')).not.toMatch(/^#/);
+    expect(stripMarkdown('> quoted')).not.toMatch(/^>/);
+  });
+
+  test('strips emphasis markers but keeps the inner text', () => {
+    expect(stripMarkdown('this is **very** _important_')).toMatch(/this is very important/);
+    expect(stripMarkdown('this is **very** _important_')).not.toMatch(/[_*]/);
+  });
+
+  test('handles empty / non-string input', () => {
+    expect(stripMarkdown('')).toBe('');
+    expect(stripMarkdown(null)).toBe('');
+    expect(stripMarkdown(undefined)).toBe('');
+    expect(stripMarkdown(42)).toBe('');
+  });
+});
+
+describe('splitSentences', () => {
+  test('splits on . ! ?', () => {
+    expect(splitSentences('Hello. World! Are you there?')).toEqual([
+      'Hello.',
+      'World!',
+      'Are you there?',
+    ]);
+  });
+
+  test('returns [] for empty / non-prose input', () => {
+    expect(splitSentences('')).toEqual([]);
+    expect(splitSentences(null)).toEqual([]);
+    expect(splitSentences('   ')).toEqual([]);
+    expect(splitSentences('---')).toEqual([]);
+  });
+
+  test('drops fragments without letter content', () => {
+    expect(splitSentences('Real sentence. !!! Another one.')).toEqual([
+      'Real sentence.',
+      'Another one.',
+    ]);
+  });
+});
+
+describe('countSyllablesInWord', () => {
+  test('counts short words as 1 syllable', () => {
+    expect(countSyllablesInWord('a')).toBe(1);
+    expect(countSyllablesInWord('cat')).toBe(1);
+  });
+
+  test('counts common English words correctly', () => {
+    expect(countSyllablesInWord('hello')).toBe(2);
+    expect(countSyllablesInWord('world')).toBe(1);
+    expect(countSyllablesInWord('beautiful')).toBeGreaterThanOrEqual(2);
+    expect(countSyllablesInWord('reading')).toBeGreaterThanOrEqual(2);
+  });
+
+  test('handles words ending in silent e', () => {
+    expect(countSyllablesInWord('make')).toBe(1);
+    expect(countSyllablesInWord('made')).toBe(1);
+  });
+
+  test('returns 0 for non-word / empty input', () => {
+    expect(countSyllablesInWord('')).toBe(0);
+    expect(countSyllablesInWord('   ')).toBe(0);
+    expect(countSyllablesInWord(null)).toBe(0);
+  });
+});
+
+describe('countSyllables / countWords', () => {
+  test('counts syllables and words for a known sentence', () => {
+    const prose = 'The quick brown fox jumps over the lazy dog';
+    expect(countWords(prose)).toBe(9);
+    // The dog has ~1 syll; "quick" 1; "brown" 1; "jumps" 1; "over" 2; "lazy" 2;
+    // "the" 1; "fox" 1. Total 11 (within ±2 of any heuristic).
+    expect(countSyllables(prose)).toBeGreaterThanOrEqual(9);
+    expect(countSyllables(prose)).toBeLessThanOrEqual(13);
+  });
+});
+
+describe('computeStats', () => {
+  test('returns zeros for an empty document', () => {
+    const s = computeStats('');
+    expect(s.wordCount).toBe(0);
+    expect(s.sentenceCount).toBe(0);
+    expect(s.readingTimeMinutes).toBe(0);
+    expect(s.fleschKincaidGrade).toBeNull();
+  });
+
+  test('handles non-string input safely', () => {
+    const s = computeStats(null);
+    expect(s.wordCount).toBe(0);
+  });
+
+  test('computes word count, reading time, grade for real prose', () => {
+    const md = `# Title
+
+The quick brown fox jumps over the lazy dog. This sentence has eight words total.
+
+\`\`\`js
+// not counted
+const x = 1;
+\`\`\`
+
+A second paragraph with [a link](https://x.com) and **bold** words.`;
+    const s = computeStats(md);
+    expect(s.wordCount).toBeGreaterThan(15);
+    // Code block is excluded
+    expect(s.wordCount).toBeLessThan(30);
+    // Reading time at 220 wpm: 24 words ≈ 0.11 min
+    expect(s.readingTimeMinutes).toBeGreaterThan(0);
+    expect(s.readingTimeMinutes).toBeLessThan(1);
+    // Grade level is a number for prose with at least one sentence
+    expect(typeof s.fleschKincaidGrade).toBe('number');
+    expect(s.sentenceCount).toBeGreaterThanOrEqual(2);
+  });
+
+  test('reading time scales with word count', () => {
+    const one = '# Title\n\nThe quick brown fox.';
+    const two = '# Title\n\n' + 'The quick brown fox. '.repeat(10);
+    expect(computeStats(two).readingTimeMinutes).toBeGreaterThan(
+      computeStats(one).readingTimeMinutes
+    );
+  });
+
+  test('honors a custom wordsPerMinute', () => {
+    const md = 'word '.repeat(220);
+    const s = computeStats(md, { wordsPerMinute: 100 });
+    expect(s.readingTimeMinutes).toBeGreaterThan(2);
+  });
+
+  test('falls back to default wpm when given an invalid value', () => {
+    const s1 = computeStats('word '.repeat(220));
+    const s2 = computeStats('word '.repeat(220), { wordsPerMinute: 0 });
+    expect(s2.readingTimeMinutes).toBe(s1.readingTimeMinutes);
+  });
+
+  test('charCount excludes whitespace', () => {
+    const s = computeStats('  hello   world  ');
+    expect(s.charCount).toBe(10); // "helloworld"
+  });
+});