Address code review feedback

Co-authored-by: benfoxall <51385+benfoxall@users.noreply.github.com>

Author: Copilot

_sass/_style.scss

@@ -5,6 +5,7 @@
   --background-light: #e6e7e8;
   --foreground: #000;
   --foreground-light: #fff;
+  --foreground-muted: #666;
   --link: blue;
   --filter: invert(0);
 }
@@ -112,7 +113,7 @@ ol {
 	display: block;
 	min-height: 1.5em;
 	font-size: 1rem;
-	color: #666;
+	color: var(--foreground-muted);
 	font-style: italic;
 	margin-top: 0.25em;
 	opacity: 0;

assets/prompt-api-summaries.js

@@ -11,6 +11,9 @@
 (function() {
   'use strict';
 
+  // Default prompt for generating summaries
+  const DEFAULT_PROMPT = 'Write a short, witty one-sentence summary of this hack day (max 10 words):';
+
   // Store parsed feed items for reuse
   let feedItems = null;
   // Store the language model session
@@ -126,18 +129,27 @@ Don't use emojis. Don't start with "A" or "The".`
    * @returns {HTMLElement|null}
    */
   function findTaglineElement(url) {
-    // Extract the path from the URL (e.g., "/hacks/50/" from "https://remotehack.space/hacks/50/")
-    const urlPath = new URL(url).pathname;
-    
-    // Find the link that matches this path
-    const links = document.querySelectorAll('.past-events a');
-    for (const link of links) {
-      const linkPath = new URL(link.href).pathname;
-      if (linkPath === urlPath) {
-        // Find the tagline element within the same list item
-        const li = link.closest('li');
-        return li?.querySelector('.hack-tagline');
+    // Validate URL before processing
+    if (!url || typeof url !== 'string') {
+      return null;
+    }
+
+    try {
+      // Extract the path from the URL (e.g., "/hacks/50/" from "https://remotehack.space/hacks/50/")
+      const urlPath = new URL(url).pathname;
+      
+      // Find the link that matches this path
+      const links = document.querySelectorAll('.past-events a');
+      for (const link of links) {
+        const linkPath = new URL(link.href).pathname;
+        if (linkPath === urlPath) {
+          // Find the tagline element within the same list item
+          const li = link.closest('li');
+          return li?.querySelector('.hack-tagline');
+        }
       }
+    } catch (error) {
+      console.warn('[Prompt API] Invalid URL in feed item:', url);
     }
     return null;
   }
@@ -177,7 +189,7 @@ Content: ${item.description}`;
    * Update all taglines on the page with generated summaries
    * @param {string} prompt - The prompt to use for generation
    */
-  async function updateTaglines(prompt = 'Write a short, witty one-sentence summary of this hack day (max 10 words):') {
+  async function updateTaglines(prompt = DEFAULT_PROMPT) {
     const available = await isPromptAPIAvailable();
     if (!available) {
       console.info('[Prompt API] Skipping tagline updates - API not available');