Mark overdrive as beta, remove product-level suggestions

Skill changes:
- Remove real-time collaboration section (product decision, not UI)
- Remove service workers / offline-first (product decision)
- Remove SharedArrayBuffer (too niche)
- Replace "application architecture" section with "performance-critical
  UI" — focused on making existing features feel fast
- Add explicit note: this skill enhances how UI FEELS, not what a
  product DOES

Beta label:
- Add betaCommands list to data.js
- Show BETA badge on /overdrive in command palette
- Show β symbol on periodic table element
- Show BETA badge on cheatsheet page

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/css/workflow.css

@@ -78,6 +78,20 @@
   font-weight: 500;
 }
 
+.beta-badge {
+  font-family: var(--font-body);
+  font-size: 0.55rem;
+  font-weight: 600;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+  color: var(--color-accent);
+  border: 1px solid var(--color-accent);
+  border-radius: 3px;
+  padding: 1px 5px;
+  vertical-align: middle;
+  margin-left: 6px;
+}
+
 .manual-cmd-desc {
   font-size: 1rem;
   line-height: 1.6;