[WIP] feat: sampler instrument — load and play audio samples chromatically

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

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This section details on the original issue you should resolve

<issue_title>feat: sampler instrument — load and play audio samples chromatically</issue_title>
<issue_description>Basic sampler: load WAV, map across keyboard, ADSR envelope.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes feat: sampler instrument — load and play audio samples chromatically #213

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[ChuxiJ]

Closing Copilot WIP — Claude Code/Codex taking over.