chore(site,readme): drop start-page meta sentence and rename "Hero" section (#16)

- site/index.html: remove "This page is the start page for the repo & software."
  lede sentence — it's redundant on the page itself and reads awkwardly to
  visitors. Keep the three-command intro.
- README.md / site/README.md: rename "Hero website / start page" →
  "Project website / start page". "Hero" is web-design jargon; casual
  readers won't know what it means.

SEO/social meta package untouched; scripts/check_site.sh still passes.

Co-authored-by: Claude <claude@anthropic.com>

Author: StewAlexander-com

README.md

@@ -45,7 +45,7 @@ laptop.
 
 ---
 
-## Hero website / start page
+## Project website / start page
 
 The project's **start page** is published on GitHub Pages:
 

site/README.md

@@ -1,4 +1,4 @@
-# Hero website / start page
+# Project website / start page
 
 A small static landing page for Python Tutor. It mirrors the app's
 dark / amber aesthetic and explains the local-first loop without

site/index.html

@@ -285,8 +285,8 @@ <h2 class="section__title">See it.</h2>
       <div class="start__inner">
         <h2 class="section__title">Clone, install, run.</h2>
         <p class="section__lede">
-          This page is the start page for the repo &amp; software. Three short
-          commands and you're at <code>http://localhost:8001/</code>.
+          Three short commands and you're at
+          <code>http://localhost:8001/</code>.
           macOS or Linux. Python 3.10+.
         </p>