feat: Start/End and Reverse Parameters for Tone.Sampler

[LoopBraker]

Summary

This PR extends Tone.Sampler with two new features that enable more flexible sample playback, inspired by Autotel:

1. Start/End Parameters for triggerAttack

Added optional start and end parameters to triggerAttack() allowing playback of specific portions of a sample without requiring loop mode.

// Play from 0.5s to 2.0s of the sample
sampler.triggerAttack("C4", Tone.now(), 1, 0.5, 2.0);

Signature change:

triggerAttack(
  notes: Frequency | Frequency[],
  time?: Time,
  velocity?: NormalRange,
  start?: Time,    // NEW: optional start offset in seconds
  end?: Time       // NEW: optional end offset in seconds
): this

2. Reverse Playback Support

Added a reverse property that plays samples backwards. When combined with start/end parameters, the offsets are automatically recalculated to maintain intuitive behavior.

sampler.reverse = true;
sampler.triggerAttack("C4"); // Plays the sample in reverse

Implementation Details

• Uses ToneBufferSource's existing start and playbackRate capabilities
• Reverse mode temporarily reverses the buffer, plays it, then restores it
• All existing Sampler functionality remains unchanged (100% backward compatible)
• Attack/release envelope still applies normally

New Example

Added samplerRange.html demonstrating:

• File upload for custom samples
• Interactive waveform visualization with zoom
• Start/end range selection with visual overlay
• Reverse toggle
• Envelope visualization (attack/release curves)
• Auto-fit selection toggle

[codecov]

Codecov Report

❌ Patch coverage is 56.71642% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.85%. Comparing base (d27e6c1) to head (e38bc2c).
⚠️ Report is 21 commits behind head on dev.

Files with missing lines	Patch %	Lines
Tone/instrument/Sampler.ts	56.72%	29 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1397      +/-   ##
==========================================
- Coverage   98.98%   98.85%   -0.13%     
==========================================
  Files         204      204              
  Lines       23138    23211      +73     
  Branches     1017     1027      +10     
==========================================
+ Hits        22901    22943      +42     
- Misses        237      268      +31     

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