Add throwaway rocket throbber prototype

[maxBRT]

Summary

• Adds an independently demoable full-screen TUI throbber prototype (ship throbber) for future per-phase waits
• Vertical rocket-in-space scene with twin exhaust, sparse starfield, and bottom phase/elapsed HUD (zero deps, TTY-aware)
• Explicitly throwaway under internal/throbber/prototype; not wired into the Run loop yet

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