Colab Shell v2.1.1

Colab Shell: Notebook & TTY (v2.1.1) fixes the long-standing "dead session" bug where leaving a session idle for hours caused new terminal tabs and file operations to fail with 404s, plus brings seamless in-app update notifications, a top-right version chip, and onboarding UI refinements.

🔄 Session Auto-Heal & Token Refresh (Headline Fix)

• Sessions no longer die after hours idle — Google Colab's runtime proxy tokens expire after a few hours even while the VM remains active. Colab Shell now automatically syncs and refreshes the token on app resume, session sync, and on-demand.
• Terminal tab resilience — Opening a new terminal tab or reconnecting to existing tabs now heals expired tokens on 404 and connects cleanly instead of throwing connection errors.
• File Explorer self-healing — Browsing, uploading, and downloading files now automatically re-authenticates if the proxy token expired during a long session.
• Kernel execution guard — Code execution and kernel restart no longer delete a live session when encountering a stale proxy token.

🔔 In-App Updates & Version Notifications

• Top-right version chip — A clean version pill in the top-right header displays your current version and automatically flips to an "Update: vX.X.X Available!" badge when a new build is published.
• Always-accessible changelog dialog — Tapping the version chip or the Settings version row opens a two-mode changelog: view offline release notes when up-to-date with a live "Check for Updates" button, or direct platform download buttons (Google Play / GitHub APK) when an update is available.

🎨 Onboarding & UI Polish

• Ergonomic Auth Buttons — Fixed Google Sign-In and code verification buttons in onboarding to standard width instead of stretching across the entire desktop/tablet screen.
• Centered responsive presentation — Onboarding slides and navigation are now neatly centered on wider viewports.