Improve generated show choreography and timing

[linear]

Outcome

Improve AI-assisted and deterministic show generation so results have clearer musical structure, recurring motifs, safer launch spacing and stronger finales.

Delivered in Sprint 5

• Added explicit prompt constraints and post-generation quality checks.
• Improved beat-grid density, moment grouping, recurring motifs and finale shaping.
• Separated launch spacing from visual duration.
• Added focused regression coverage for choreography quality, prompt constraints, motifs, timing and launch-position layout.

Evidence

• PR feat: improve generated show choreography and timing #368, merged 31 August 2026
• Commit 9f7749e
• 33 files changed with 1,741 additions and targeted generation tests

Boundary

This records implementation delivery. Representative-song evaluation and the remaining analysis-to-cue regression work stay tracked separately in #218.