feat: add generic setCtl(name, value) to ChiptuneJsPlayer

[indigo423]

Summary

Adds a generic setCtl(name, value) method to ChiptuneJsPlayer and a matching 'setCtl' case in the worklet's handleMessage_. Mirrors the existing setPitch / setTempo shape — same stackSave / stackRestore bracketing, same fail-quiet guard.

Why

There's currently no main-thread path to set a libopenmpt control value that doesn't already have a dedicated wrapper. Consumers who need a knob outside the existing setPitch / setTempo / setStereoSeparation set have to fork the worklet.

The most common real-world case is overriding the hardcoded render.resampler.emulate_amiga defaults that play() stamps onto every new module (chiptune3.worklet.js:212–219). Today those defaults are pinned to emulate_amiga="1" + emulate_amiga_type="a1200" and there's no way to expose them as a user-facing setting — the only escape is recreating the ChiptuneJsPlayer instance, which destroys the AudioContext, reloads the worklet, and gives the listener half a second of silence on every toggle.

setCtl fills the gap without committing the class API to one specific control. Name and value are passed as strings, the same encoding libopenmpt's own ctl interface expects.

Use case

CoolModFiles.com is a web-based Amiga MOD player. We want a three-state Amiga emulation toggle in the player UI — Off (modern clean resampler) / A500 (warm, ~4.9 kHz analogue filter) / A1200 (bright, ~28 kHz filter) — letting listeners A/B the sound character of two real Amiga hardware models against libopenmpt's modern path. The toggle has to work mid-track without audio interruption, which means the existing 'rebuild the player' workaround is unacceptable.

With setCtl, the toggle is two ctl_set calls and an audible filter change on the next render block:

player.setCtl('render.resampler.emulate_amiga', '1')
player.setCtl('render.resampler.emulate_amiga_type', 'a500')

The Amiga emulation toggle is already live at mods.amiga.fans, currently riding a local fork of this patch.

Diff

+15 lines, 2 files. No new dependencies, no API removals, no behaviour changes for existing consumers.

• chiptune3.js: setCtl(name, value) { this.postMsg('setCtl', { name, value }) } placed next to setTempo.
• chiptune3.worklet.js: new case 'setCtl' in handleMessage_ placed next to setTempo.

Notes

• .min.js siblings are not regenerated in this PR — assuming minify.js runs as part of a release cut. Happy to include them if you'd prefer.
• The branch is forked off v3 (current default).

Thanks for chiptune — it's the audio backbone of our site.