[Feature]: Re-enable update available notification #9

Problem or opportunity

The update notification for new Diffex releases is currently suppressed in the interactive startup UI.
Users and maintainers need a tracked follow-up so the notification can be re-enabled intentionally after the current UI pass.

Desired outcome

When the team is ready, interactive mode should display the existing "Update Available" notification again for newer Diffex releases.
The existing version-check and notification rendering code should remain usable.

Success criteria

• The update notification display gate is re-enabled or replaced by an equivalent rollout mechanism.
• The interactive startup UI shows the update message only when a newer Diffex release is detected.
• A focused test or harness check covers the expected display behavior.

Affected area

tui

Proposed approach

Review DIFFEX_UPDATE_AVAILABLE_NOTIFICATION_ENABLED in packages/coding-agent/src/modes/interactive/interactive-mode.ts and re-enable the call to showNewVersionNotification.

Alternatives considered

Leaving the notification hidden indefinitely would remove useful upgrade visibility for users.

Additional context

Created while suppressing the notification display for the TUI startup cleanup on branch feat/tui-intro-cleanup.

Pre-submission checks

• I searched existing issues and did not find a duplicate request.
• I described the need and desired outcome, not only a preferred implementation.
• I did not include secrets, credentials, or private deployment details.