v1.0.5 — Seamless track regen

Fix

Audio no longer stutters when the next track is being generated in shuffle or Auto-DJ regen. The Tone.js synths for the incoming track are now built into a side pool while the current track is still playing, so the bar-boundary swap is just a pointer promotion — no new Tone.Synth() on the audio-scheduling thread.

Technical

• New tone-engine methods: preloadInstrument(ch, name), promotePooledInstrument(ch, name), clearPool()
• preview-ready handler walks the incoming project's nets and preloads each (channel, instrument) serially
• _applyProjectInstruments and _onInstrumentsChanged try pool promotion before falling back to cold load

The "seamless swap" comment now matches reality.