🎛️ Chord: better channel mixing

[ScottMorris]

• 💡 What: Assigned distinct waveforms per channel (triangle for bass, sawtooth for drums, square for lead) instead of using square waves for everything.
• 🎯 Why: Improves procedural music mix, giving each layer its own texture and preventing the entire track from sounding like crunchy stale bread.
• 🔊 How to hear it: Launch the game, press Space to start music, and listen to the distinct bassline vs. the high squeaks and drum hits.

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PR created automatically by Jules for task 442584947227346527 started by @ScottMorris

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