Document the staged single-route showcase and presenter flow

roadscore/SHOWCASE.md

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+# Replay showcase operator flow
+
+Scope as of September 20: one showcase route, current ACE/Prism, replay only. Freeze live-car work and unrelated feature development. Preserve the gold excerpt and accepted soundtrack archives. The operator is back at the event. Hardware inspection is allowed for the designated owner; current access must be verified before claiming readiness. No device behavior should be inferred from the local rehearsal recording.
+
+On the event comma, while offroad:
+
+```sh
+./onroad --roadscore route1
+```
+
+The private local favorites file resolves route1 to showcase E and route2 to backup A. No private route identities belong in this document. Normal launches use a fresh logged session seed; explicit `--roadscore-seed` is a diagnostic override. Current native operation uses prepared generic role conditioning and fresh ACE sampling, not a fresh semantic-planner pass per launch.
+
+In Galaxy's RoadScore section, replay-only **Simulate disengage**, **Simulate engage**, and **Use recorded state** affect music presentation only. They require a fresh matching replay session and offroad state. They do not engage openpilot or modify vehicle controls. Their source/deployment checks do not establish an audible physical test. Verify one cycle before using them with judges. Proposed rehearsal: contain at 0:10, open at 0:15, recorded state at 0:19; avoid overlapping the first signal motif.
+
+Use the protected recorded fallback if preparation or hardware is unreliable. The local rehearsal package is `Desktop/RoadScore/demos/showcase-rehearsal/`; `SHOW DEMO.command` opens the route E presentation cut over matching camera footage: 5:00.35, unchanged soundtrack until a two-second closing fade. The unedited exact soundtrack remains protected. The full judge briefing, evidence inventory, timestamp script, and cheat sheet are in that package. This is recorded playback, not fresh generation. The original 315.4-second recording includes an approximately 15-second historical EOF tail; the source app ended with an input-stall error despite uninterrupted audio. It is not the latest device run and has neither native UI nor the newest presentation refinements.
+
+Do not infer audible accents from source alerts alone. In the locked soundtrack, the first strong signal motif begins about 0:24.6, curve payoffs occur around 0:52.7 and 2:01.3, and recorded engagement switches at 2:10.8 and 2:15.9. Fresh generations may have different beat phase. Let the music establish and leave silence around those demonstrations.
+
+If anything fails, switch to the labeled recording or the approved 30-second stopped-motion comparison; do not change vehicle controls, model settings or power limits during judging. Current live-car readiness is not established. Physical Bluetooth synchronization and new replay-button operation still need a device check when access resumes.
+
+## Presentation
+
+Lead with: “RoadScore makes the drive part of the music.” Explain the model/runtime split before playback, then leave silence for the melody, signal motif and curve payoff. The core line is: “The model composes ahead; the presentation layer reacts now.” Use the local SPEAKING_CARD.md and TODAY_RUN_SHEET.md for the timestamped presenter flow.
+
+Advance knowledge is allowed for this staged showcase. Keep the recorded source events real and disclose manual music simulation. Do not change ordinary fresh-seed behavior or official judging policy to make this presentation repeatable. A route-specific demonstration does not prove arbitrary-route or live-car readiness.