v1.0.0-rc4

Update awareness — the surface this very screen builds on.

• Update-available notifications across all surfaces — the cockpit, CLI, and status surfaces now tell you when a newer FlowForge release is published, with the one-line update command always in reach (#2250).
• Release notes overlay — press N in the cockpit to read the newest version's release notes, rendered with glamour in a scrollable view.
• Heartbeat banner softening — the heartbeat banner is quieter and less intrusive (#2250).