docs: add starter mdx posts

content/posts/math-notes-for-builders.mdx

@@ -0,0 +1,33 @@
+---
+title: "Math Notes for Builders"
+date: "2026-05-08"
+excerpt: "A compact starter post that keeps Math and Code tags populated while checking equation rendering."
+tags:
+  - Math
+  - Code
+  - Web Dev
+author: "Starter Content"
+---
+
+This replaceable note exists to keep the **Math**, **Code**, and **Web Dev** tag pages meaningful during early validation.
+
+## Tiny model
+
+Inline math can express a quick estimate like $n \log n$, while display math can show the full relationship:
+
+$$
+T(n) = O(n \log n) + O(k)
+$$
+
+## Practical reminder
+
+- Prefer simple explanations before formulas.
+- Add runnable code when it clarifies an idea.
+- Link back to related posts, such as the [starter showcase](/posts/starter-mdx-showcase/).
+
+```js title="estimate.js" {1,4}
+export function estimate(items, constant = 1) {
+  const n = Math.max(items.length, 1)
+  return n * Math.log2(n) + constant
+}
+```