fix: load factory synth presets without CommonJS require in the browser

[beejsbj]

Description

Selecting a factory synth preset in the browser throws before the preset can be applied. loadSynthPreset calls CommonJS require("./uiStore") from the browser bundle, where require is not defined. Legacy preset identifiers such as piano, lead, strings, pad, and bass work because they bypass this action.

Tested commit: 2bebdd2cbaaef1092a06ff613c7868c9f3bd4b6c.

Steps to Reproduce

1. Start the web app and create or select a piano-roll track.
2. Open the synth preset browser.
3. Select the factory preset Sub Bass (factory-sub-bass), or call:

window.__store.getState().loadSynthPreset(trackId, "factory-sub-bass")

4. Inspect the console and the track state.

Expected Behavior

The selected factory preset is applied to the track and updates its instrument/preset fields without a runtime error.

Actual Behavior

The action throws:

ReferenceError: require is not defined

No factory preset is applied.

Environment

• Browser: Google Chrome 147.0.7727.101 (headless Playwright)
• OS: Ubuntu 24.04.3 LTS
• Node version: 24.13.0
• Audio path: web / Tone.js

Screenshots / Logs

loadSynthPreset invokes require("./uiStore") despite the project being ESM/browser code. The factory preset ID is defined in synthPresets.ts.

Acceptance Criteria

• Selecting factory-sub-bass from the preset browser applies it without ReferenceError.
• Calling loadSynthPreset(trackId, "factory-sub-bass") from the exposed store action updates the track deterministically.
• Factory and user preset lookup still works in the browser build.
• A browser-facing regression test covers loading at least one factory preset.
• Fix passes all quality gates.