fix(workspace): single scroll area, drag cleanup, thin note titles with bundled Inter

- the workspace fills the window; only the note scrolls (also on phones, where the
  sideways scroll area used to scroll on its own)
- clear drag state on dragend, calmer sidebar toggle when collapsed
- ship Inter as variable font, light and larger note titles; header shows the
  title only after the big title scrolled away and stays one row on phones
- main builds show the package version without -dev

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/index.css

@@ -28,7 +28,7 @@
 body {
   background-color: var(--bg-app);
   color: var(--text-main);
-  font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+  font-family: 'Inter Variable', 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
   overflow-x: hidden;
   transition: background-color 140ms ease, color 140ms ease;
 }