Remove prompts from website

Remove the prompts page, navigation link, homepage card, and all
references to prompts across the website source code. The repo no
longer contains prompt files, so the website should not reference them.

Files removed:
- website/src/pages/prompts.astro
- website/src/scripts/pages/prompts.ts

Files updated:
- BaseLayout.astro: remove nav link and update description
- index.astro: remove prompts card and update text
- llms.txt.ts: remove prompts import and section
- plugins.astro: update description text
- utils.ts: remove prompt type from install config, icons, labels
- pages/index.ts: remove prompts from counts
- modal.ts: update JSDoc comment

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

website/src/pages/index.astro

@@ -11,7 +11,7 @@ const base = import.meta.env.BASE_URL;
     <section class="hero" aria-labelledby="hero-heading">
       <div class="container">
         <h1 id="hero-heading">Awesome GitHub Copilot</h1>
-        <p class="hero-subtitle">Community-contributed instructions, prompts, agents, and skills to enhance your GitHub Copilot experience</p>
+        <p class="hero-subtitle">Community-contributed agents, instructions, and skills to enhance your GitHub Copilot experience</p>
         <div class="hero-search">
           <label for="global-search" class="sr-only">Search all resources</label>
           <input type="text" id="global-search" placeholder="Search all resources..." autocomplete="off" role="combobox" aria-autocomplete="list" aria-expanded="false" aria-controls="search-results">
@@ -33,14 +33,6 @@ const base = import.meta.env.BASE_URL;
             </div>
             <div class="card-count" data-count="agents" aria-label="Agent count">-</div>
           </a>
-          <a href={`${base}prompts/`} class="card card-with-count" id="card-prompts">
-            <div class="card-icon" aria-hidden="true">🎯</div>
-            <div class="card-content">
-              <h3>Prompts</h3>
-              <p>Ready-to-use prompt templates for development tasks</p>
-            </div>
-            <div class="card-count" data-count="prompts" aria-label="Prompt count">-</div>
-          </a>
           <a href={`${base}instructions/`} class="card card-with-count" id="card-instructions">
             <div class="card-icon" aria-hidden="true">📋</div>
             <div class="card-content">
@@ -103,7 +95,7 @@ const base = import.meta.env.BASE_URL;
           <div class="step">
             <div class="step-number" aria-hidden="true">1</div>
             <h3>Browse</h3>
-            <p>Explore agents, prompts, instructions, and skills</p>
+            <p>Explore agents, instructions, skills, and plugins</p>
           </div>
           <div class="step">
             <div class="step-number" aria-hidden="true">2</div>