fix(tui): calm the live stream and hold teaching tips

[jkyberneees]

Summary

• Hold finished sentences on the live intent rail (frozen stem before the first period) so a fast thinking_delta stream cannot ticker the excerpt.
• Quiet the stream chrome: one spinner on the status line, static ▸ on live tool steps, and reasoning / composing labels so the rail and answer card own the words.
• Leave scrollback alone on wake/remote turn_started (↓ new output + ^G instead of yanking), and dwell JIT teaching tips 8s (5s longer than info traces).

Test plan

• Stream a fast thinking turn: rail holds completed sentences, then updates on the next period; Tab / ^E still opens the full block
• Watch a parallel tool swarm: transcript steps stay on ▸; only the status line spinner animates
• Scroll up mid-session, then let a wake/remote turn start: stay in history, footer shows ↓ new output, ^G jumps to latest
• Queue a prompt mid-turn (or trigger the first swarm / first multi-step turn): 💡 tip stays ~8s
• make fmt vet lint test stays green

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