Procedural Drum Synthesis Enhancements (DSP Analysis)

[Pitrat-wav]

This PR implements deep DSP-level enhancements to the procedural drum synthesis engine, following the provided research on Roland TR-808 and TR-909 emulations.

Key changes include:

1. Velocity Sensitivity: All drum models now accept a velocity parameter that scales their amplitude envelopes (VCA).
2. Analog Variance: The sequencer now triggers drums with randomized velocity (0.7 - 1.0) to simulate the "breathing" character of analog hardware.
3. Master Saturation: A new master DRIVE control on the drum bus implements a non-linear soft-clipping curve (tanh approximation) via a WaveShaperNode, as detailed in the research.
4. Improved Default Patterns: Default Euclidean settings have been updated to provide a more cohesive "drum party" experience out of the box.
5. Independent Hi-Hat Routing: Fixed a routing issue to allow separate volume control for Open and Closed Hi-Hats.
6. UI Enhancements: Added a 'DRIVE' knob to the Drums view.

Verified via TypeScript check (tsc --noEmit) and visual inspection of the UI via Playwright screenshots.

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PR created automatically by Jules for task 3205841593049366977 started by @Pitrat-wav

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