Add approvals and a sub-agent fleet to the README video

[igalshilman]

Summary

The README video (2:04) now shows three acts from one real session:

1. An ordinary turn. The model writes a program whose three web searches run at once, and is steered mid-turn. A guardrail ("Writing or changing a file in the workspace needs a person's approval first.") holds each file write. The approval is resolved from the UI's own Approvals panel.
2. A fleet of sub-agents. Four sub-agents research four cities at the same time. Each child is a whole agent, so the video tiles each child's own read-only page in a 2×2 grid, then returns to the parent's combined answer.
3. Kill it mid-turn. The same as before: kill -9 during a durable timer, restart, replay, finish.

Recorder changes in .misc/video/:

• The UI renders in its one-column layout at about 1.55× zoom for legible text. One injected rule shortens the conversation pane to fit the frame, and the view slides to the Approvals panel while a decision is pending.
• It fast-forwards at 2× only while the turn waits on a model (the badge shows it), and holds about 6.5 s on each answer.
• It steers only after the program's searches are recorded. A steer that lands mid-program hands the program off as pending work, which is a different story.
• The encode is limited-range yuv420p at level 4.1, written to a temporary file and then renamed.

Test plan

• Recorded on a fresh Restate server, and checked frames across the whole take
• The video plays from its user-attachments URL
• Check the README renders the player on GitHub

🤖 Generated with Claude Code