Complete v16.0.0: Hermes Agent support + multi-platform rebrand (#26)

Learnings applied from alirezarezvani/claude-skills: native SKILL.md agents
(Hermes, Vibe) install the files directly — no conversion — so support is a
sync script, not regenerated copies.

- scripts/sync-hermes-skills.py: stdlib installer that places skills/ into
  ~/.hermes/skills/ (copy or --link symlink, --flat, --dry-run). Hermes reads
  the same open SKILL.md standard and auto-discovers by description.
- README rebrand: title, tagline, intro, and a "works with" platforms badge now
  cover Claude, ChatGPT, Gemini, and Hermes. Works-With table splits native
  SKILL.md agents (Claude Code, Hermes) from paste-in chat LLMs. Repo name,
  marketplace ID, and install commands intentionally unchanged.
- Version bump to v16.0.0 (Multi-Platform). Note: v15.0.0 was already published
  (Skill Playground), so this release is v16.0.0; the changelog now also records
  v15.0.0 in its history. Updated README badge/What's-New, CHANGELOG, SECURITY,
  and playground tagline/meta.


Claude-Session: https://claude.ai/code/session_016JWn5jRD5tcEFKrubjQ6Px

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

web/index.html

@@ -4,7 +4,7 @@
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>Skill Playground — Product Notes</title>
-  <meta name="description" content="Run any of 170+ Claude skills from your browser with your own API key. Pick a skill tile, fill the inputs, get the output." />
+  <meta name="description" content="Run any of 170+ professional skills in your browser with your own Claude API key — or copy each one as a ready-made ChatGPT or Gemini prompt." />
   <link rel="stylesheet" href="styles.css" />
   <script src="https://cdn.jsdelivr.net/npm/marked@12.0.0/marked.min.js"></script>
   <script src="https://cdn.jsdelivr.net/npm/dompurify@3.0.9/dist/purify.min.js"></script>
@@ -15,7 +15,7 @@
       <img src="assets/product-notes.jpg" alt="Product Notes" class="brand-logo" />
       <div class="brand-text">
         <h1>Skill Playground</h1>
-        <p class="tagline">170+ Claude skills — pick one and run it with your own key.</p>
+        <p class="tagline">170+ professional skills — run with your Claude key, or copy for ChatGPT &amp; Gemini.</p>
       </div>
     </div>
     <div class="key-area">