[SlipstreamSurfer]

What changed

• Gives each bar twelve independently programmable dimmer and colour cells in a single batched MultiMesh.
• Adds held 50/50, odd/even, centre, end, solid and slow window patterns; alternating colours follow the active palette, with monochrome cues preserved.
• Adds a focused regression test and includes it in the normal build pipeline.
• Carries forward the 0.60.0-test1 show, source continuity and symmetric back towers.

Validation

• Full local Godot 4.7.2 test suite passed, including the new pixel-state checks.
• Linux, Windows and macOS packages exported; Linux smoke test passed.
• Captured a GPU render using a generated local 128 BPM test signal; review files remain ignored.

Remaining work

• Roof-bar and back-tower head additions, show-balance/comfort telemetry, and longer user review are still tracked in docs/sv-recovery-plan.md.