feat: add content collection with schema and reading-time utility

- Created src/content.config.ts with Astro defineCollection using glob loader, pattern '**/*.{md,mdx}', base './src/content/posts', and Zod schema with 5 fields (title, date, type, tags, summary)
- Created src/content/posts/ directory for content storage
- Created src/utils/reading-time.ts with getReadingTime function (split whitespace, 200 WPM, Math.max(1, Math.ceil))
- All 23 new tests pass, all 61 total tests pass, npm run build succeeds

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Co-Authored-By: Amplifier <240397093+microsoft-amplifier@users.noreply.github.com>

tests/reading-time.test.mjs

@@ -0,0 +1,53 @@
+import { describe, it } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+
+const utilPath = resolve('src/utils/reading-time.ts');
+
+function readUtil() {
+  return readFileSync(utilPath, 'utf-8');
+}
+
+describe('reading-time utility', () => {
+  it('should exist at src/utils/reading-time.ts', () => {
+    const content = readUtil();
+    assert.ok(content.length > 0, 'Utility file should not be empty');
+  });
+
+  it('should export a getReadingTime function', () => {
+    const content = readUtil();
+    assert.match(content, /export\s+(function\s+getReadingTime|const\s+getReadingTime|{[^}]*getReadingTime)/, 'should export getReadingTime');
+  });
+
+  it('should accept a text: string parameter', () => {
+    const content = readUtil();
+    assert.match(content, /getReadingTime\s*\(\s*text\s*:\s*string\s*\)/, 'should accept text: string param');
+  });
+
+  it('should return a number type', () => {
+    const content = readUtil();
+    assert.match(content, /:\s*number/, 'should have number return type');
+  });
+
+  it('should split on whitespace', () => {
+    const content = readUtil();
+    assert.match(content, /split\s*\(\s*\/\\s\+\//, 'should split on whitespace regex');
+  });
+
+  it('should divide by 200 WPM', () => {
+    const content = readUtil();
+    assert.match(content, /200/, 'should use 200 WPM');
+  });
+
+  it('should use Math.max(1, Math.ceil(...))', () => {
+    const content = readUtil();
+    assert.match(content, /Math\.max\s*\(\s*1/, 'should use Math.max(1, ...)');
+    assert.match(content, /Math\.ceil/, 'should use Math.ceil');
+  });
+
+  it('should filter empty strings from split result', () => {
+    const content = readUtil();
+    assert.match(content, /filter/, 'should filter empty strings from split');
+  });
+});