fix(conversation): back to live session from resumed history

[RonenMars]

Summary

• When the VT terminal’s “View the conversation history →” notice opens a conversation, pass fromSession so the footer knows the user came from a live session.
• Replace Resume Session with Back to Live Session, which returns to /session/:id instead of starting another resume.
• Stacked on fix(terminal): disclose missing scrollback after resume #544 (fix/resumed-terminal-scrollback-disclosure), which adds the scrollback notice.

Test plan

• Unit: conversationHref includes fromSession
• Integration: TerminalView notice navigates with fromSession
• Integration: conversation detail swaps Resume → Back to Live Session and replaces to the live session
• Manual: resume a conversation → Terminal view → tap history notice → footer shows Back to Live Session → returns to live session
• Manual: open a conversation from the hub (no fromSession) → Resume Session still shown