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/package.json

@@ -13,6 +13,7 @@
     "test:run": "vitest run"
   },
   "dependencies": {
+    "@fontsource-variable/inter": "5.3.0",
     "@types/prismjs": "^1.26.6",
     "emoji-picker-react": "4.12.0",
     "framer-motion": "^11.15.0",