memory-leak-audit

# Memory Leak Audit The #1 bug category in VS Code. This skill encodes the patterns that prevent and fix leaks. ## When to Use - Reviewing code that registers event listeners or DOM handlers - Fixing reported memory leaks (listener counts growing over time) - Creating objects in methods that are called repeatedly - Working with model lifecycle events (onWillDispose, onDidClose) - Adding event subscriptions in constructors or setup methods ## Audit Checklist Work through each check in order. A single missed pattern can cause thousands of leaked objects. ### Step 1: DOM Event Listeners **Rule**: Never use raw `.onload`, `.onclick`, or `addEventListener()` directly. Always use `addDisposableListener()`. ```typescript // BAD — leaks a listener every call this.iconElement.onload = () => { ... }; // GOOD — tracked and disposable this._register(addDisposableListener(this.iconElement, 'load', () => { ... })); ``` **Validated by**: PR #280566 — Extension icon widget leaked 185 listeners after 37 toggles. ### Step 2: One-Time Events **Rule**: Use `Event.once()` for events that should only fire once (lifecycle events, close events, first-change events). ```typescript // BAD — listener stays registered forever after first fire model.onDidDispose(() => store.dispose()); // GOOD — auto-removes after first invocation Event.once(model.onDidDispose)(() => store.dispose()); ``` **Validated by**: PRs #285657, #285661 — Terminal lifecycle hacks replaced with `Event.once()`. ### S...