fix(frontend): compact song controls

[paolino]

Summary

• Collapses cell controls into one compact strip and removes the separate cell action row.
• Collapses track gutter controls into one compact row above VOL/FLT/DLY sliders.
• Adds labeled Song and Toolbox clusters for the global top-bar actions.
• Updates the render smoke to assert the new compact structure and preserved interactions.

Validation

• ./gate.sh

Closes #37