fix(seo): shorten meta descriptions to 110-160 chars

Shorten meta descriptions to prevent truncation in search snippets.

9 pages updated:
- overview: 161 → 130 chars
- hoisting: 188 → 145 chars
- proxy-reflect: 179 → 139 chars
- tagged-template-literals: 168 → 124 chars
- intersection-observer: 175 → 136 chars
- typed-arrays-arraybuffers: 164 → 120 chars
- custom-events: 161 → 125 chars
- performance-observer: 196 → 130 chars
- mutation-observer: 178 → 120 chars

Per ahrefs SEO recommendation: descriptions should be 110-160 chars.

Author: leonardomso

docs/beyond/concepts/custom-events.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Custom Events in JavaScript"
 sidebarTitle: "Custom Events"
-description: "Learn JavaScript custom events. Create, dispatch, and listen for CustomEvent, pass data with the detail property, and build decoupled event-driven architectures."
+description: "Learn JavaScript custom events. Create and dispatch CustomEvent, pass data with detail, and build event-driven architectures."
 ---
 
 What if you could create your own events, just like `click` or `submit`? What if a shopping cart could announce "item added!" and any part of your app could listen and respond? How do you build components that communicate without knowing about each other?

docs/beyond/concepts/hoisting.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Hoisting in JavaScript"
 sidebarTitle: "Hoisting: How Declarations Move to the Top"
-description: "Learn JavaScript hoisting and how declarations are moved to the top of their scope. Understand var vs let vs const hoisting, function hoisting, the Temporal Dead Zone, and common pitfalls."
+description: "Learn JavaScript hoisting: how var, let, const, and function declarations are moved to the top of their scope. Understand the Temporal Dead Zone."
 ---
 
 Why can you call a function before it appears in your code? Why does `var` give you `undefined` instead of an error, while `let` throws a `ReferenceError`? How does JavaScript seem to know about variables before they're declared?

docs/beyond/concepts/intersection-observer.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Intersection Observer in JavaScript"
 sidebarTitle: "Intersection Observer"
-description: "Learn the Intersection Observer API in JavaScript. Detect element visibility, implement lazy loading, infinite scroll, and scroll animations efficiently without scroll events."
+description: "Learn the Intersection Observer API in JavaScript. Implement lazy loading, infinite scroll, and scroll animations without scroll events."
 ---
 
 How do you know when an element scrolls into view? How can you lazy-load images only when they're about to be seen? How do infinite-scroll feeds know when to load more content? And how can you trigger animations at just the right moment as users scroll through your page?

docs/beyond/concepts/mutation-observer.mdx

@@ -1,7 +1,7 @@
 ---
 title: "MutationObserver in JavaScript"
 sidebarTitle: "MutationObserver: Watching DOM Changes"
-description: "Learn the MutationObserver API in JavaScript. Understand how to watch DOM changes, detect attribute modifications, observe child elements, and build reactive UIs without polling."
+description: "Learn the MutationObserver API in JavaScript. Watch DOM changes, detect attribute modifications, and build reactive UIs."
 ---
 
 How do you know when something changes in the DOM? What if you need to react when a third-party script adds elements, when user input modifies content, or when attributes change dynamically?

docs/beyond/concepts/performance-observer.mdx

@@ -1,7 +1,7 @@
 ---
 title: "PerformanceObserver in JS"
 sidebarTitle: "Performance Observer"
-description: "Learn the Performance Observer API in JavaScript. Understand how to measure page performance, track Long Tasks, monitor layout shifts, and collect Core Web Vitals metrics for real user monitoring."
+description: "Learn the Performance Observer API in JavaScript. Measure page performance, track Long Tasks, and collect Core Web Vitals metrics."
 ---
 
 How do you know if your website is actually fast for real users? You might run Lighthouse once, but what about the thousands of visitors with different devices, network conditions, and usage patterns? Without real-time performance monitoring, you're flying blind.

docs/beyond/concepts/proxy-reflect.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Proxy & Reflect in JavaScript"
 sidebarTitle: "Proxy & Reflect: Intercepting Object Operations"
-description: "Learn JavaScript Proxy and Reflect APIs. Understand how to intercept object operations, create reactive systems, implement validation, and build powerful metaprogramming patterns."
+description: "Learn JavaScript Proxy and Reflect APIs. Intercept object operations, create reactive systems, and build powerful metaprogramming patterns."
 ---
 
 What if you could intercept every property access on an object? What if reading `user.name` could trigger a function, or setting `user.age = -5` could throw an error automatically?

docs/beyond/concepts/tagged-template-literals.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Tagged Template Literals"
 sidebarTitle: "Tagged Template Literals"
-description: "Learn JavaScript tagged template literals. Understand how tag functions work, access raw strings, build HTML sanitizers, create DSLs, and use String.raw for file paths."
+description: "Learn JavaScript tagged template literals. Understand tag functions, access raw strings, and build HTML sanitizers and DSLs."
 ---
 
 How do libraries like GraphQL and Lit HTML let you write special syntax inside JavaScript template literals? How can a function intercept and transform template strings before they become a final value?

docs/beyond/concepts/typed-arrays-arraybuffers.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Typed Arrays in JavaScript"
 sidebarTitle: "Typed Arrays & ArrayBuffers"
-description: "Learn JavaScript Typed Arrays and ArrayBuffers. Understand binary data handling, DataView, working with WebGL, file processing, and network protocol implementation."
+description: "Learn JavaScript Typed Arrays and ArrayBuffers for binary data handling. Work with DataView, WebGL, and file processing."
 ---
 
 How do you process a PNG image pixel by pixel? How do you read binary data from a WebSocket? How does WebGL render millions of triangles efficiently?

docs/beyond/getting-started/overview.mdx

@@ -1,7 +1,7 @@
 ---
 title: "Beyond 33: Extended JavaScript Concepts"
 sidebarTitle: "Overview"
-description: "Go deeper into JavaScript with 29 advanced concepts that build on the original 33. Master topics like hoisting, proxies, observers, and performance optimization."
+description: "Go beyond the original 33 with 29 advanced JavaScript concepts. Master hoisting, proxies, observers, and performance optimization."
 ---
 
 You've learned the fundamentals. Now it's time to go deeper.