Drop dead SvelteResizeObserver from libs/dom

`SvelteResizeObserver` lived in `$libs/dom` as a generic ResizeObserver
wrapper with manual `refresh()` / `destroy()` lifecycle. Across the
repo it had zero real consumers — only its own test file imported it.
The Svelte-aware ResizeObserver in active use is `ResizeObserver$` in
`src/suix/soma/layers/resize-observer.svelte.ts`, which uses `$effect`
for auto-cleanup and is consumed by accordion.

Removing the unused module keeps `$libs/dom` honest as "the surface
nobody can reach for a duplicate ResizeObserver implementation when
they could just consume the soma layer (or, eventually, an `$adom`
helper that mirrors `BodyScrollLock`)".

Verification:
- `npx vitest run src/libs/dom src/arts/adom`: 9 / 9 files, 37 / 37
  tests green (down from 10 / 40 — the dropped 3 tests covered the
  removed class).
- `node scripts/check-aliases.mjs`: clean (only the pre-existing
  PERMUTATION_RUNNER.md hit, unrelated).
- `npm run check`: 61 / 0 / 17 unchanged from before (the residual
  errors are all in untracked src/suix/* and predate this commit).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/libs/dom/index.ts

@@ -4,6 +4,5 @@ export * from './core'
 export * from './errors'
 export * from './focus'
 export * from './locale'
-export * from './resize-observer'
 export * from './responsive'
 export * from './tabbable'

src/libs/dom/resize-observer.ts

@@ -1,58 +0,0 @@
-export type ResizeObservedNode = HTMLElement | null | undefined
-export type ResizeObservedNodeGetter = () => ResizeObservedNode
-
-function canObserveResize(): boolean {
-	return typeof window !== 'undefined' && typeof ResizeObserver !== 'undefined'
-}
-
-export class SvelteResizeObserver {
-	readonly node: ResizeObservedNodeGetter
-	readonly onResize: () => void
-
-	private observer: ResizeObserver | null = null
-	private observedNode: HTMLElement | null = null
-	private rAF = 0
-
-	constructor(node: ResizeObservedNodeGetter, onResize: () => void) {
-		this.node = node
-		this.onResize = onResize
-		this.refresh()
-	}
-
-	refresh = () => {
-		if (!canObserveResize()) return
-
-		const nextNode = this.node() ?? null
-		if (nextNode === this.observedNode) return
-
-		this.disconnect()
-		if (!nextNode) return
-
-		this.observedNode = nextNode
-		this.observer = new ResizeObserver(() => {
-			if (typeof window.requestAnimationFrame === 'function') {
-				window.cancelAnimationFrame(this.rAF)
-				this.rAF = window.requestAnimationFrame(this.onResize)
-				return
-			}
-
-			this.onResize()
-		})
-
-		this.observer.observe(nextNode)
-	}
-
-	destroy = () => {
-		this.disconnect()
-	}
-
-	private disconnect() {
-		if (typeof window !== 'undefined' && typeof window.cancelAnimationFrame === 'function') {
-			window.cancelAnimationFrame(this.rAF)
-		}
-		this.rAF = 0
-		this.observer?.disconnect()
-		this.observer = null
-		this.observedNode = null
-	}
-}

src/libs/dom/test/resize-observer.test.ts

@@ -1,102 +0,0 @@
-// @vitest-environment jsdom
-
-import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
-
-import { SvelteResizeObserver } from '../resize-observer';
-
-type ResizeObserverCallbackLike = ConstructorParameters<typeof ResizeObserver>[0];
-
-class MockResizeObserver {
-	static instances: MockResizeObserver[] = [];
-
-	readonly observed: Element[] = [];
-	disconnected = false;
-	readonly callback: ResizeObserverCallbackLike;
-
-	constructor(callback: ResizeObserverCallbackLike) {
-		this.callback = callback;
-		MockResizeObserver.instances.push(this);
-	}
-
-	observe = (element: Element) => {
-		this.observed.push(element);
-	};
-
-	disconnect = () => {
-		this.disconnected = true;
-	};
-
-	trigger() {
-		this.callback([] as ResizeObserverEntry[], this as unknown as ResizeObserver);
-	}
-}
-
-describe('libs/dom resize observer', () => {
-	const originalResizeObserver = globalThis.ResizeObserver;
-	const originalRequestAnimationFrame = window.requestAnimationFrame;
-	const originalCancelAnimationFrame = window.cancelAnimationFrame;
-
-	beforeEach(() => {
-		MockResizeObserver.instances = [];
-		(globalThis as typeof globalThis & { ResizeObserver: typeof ResizeObserver }).ResizeObserver =
-			MockResizeObserver as unknown as typeof ResizeObserver;
-		window.requestAnimationFrame = ((callback: FrameRequestCallback) => {
-			callback(0);
-			return 1;
-		}) as typeof window.requestAnimationFrame;
-		window.cancelAnimationFrame = vi.fn() as typeof window.cancelAnimationFrame;
-	});
-
-	afterEach(() => {
-		const globals = globalThis as { ResizeObserver?: typeof ResizeObserver };
-		if (originalResizeObserver) {
-			globals.ResizeObserver = originalResizeObserver;
-		} else {
-			delete globals.ResizeObserver;
-		}
-		window.requestAnimationFrame = originalRequestAnimationFrame;
-		window.cancelAnimationFrame = originalCancelAnimationFrame;
-	});
-
-	it('observes the provided node and invokes the callback on resize', async () => {
-		const node = document.createElement('div');
-		const onResize = vi.fn();
-
-		new SvelteResizeObserver(() => node, onResize);
-
-		expect(MockResizeObserver.instances).toHaveLength(1);
-		expect(MockResizeObserver.instances[0]?.observed).toEqual([node]);
-
-		MockResizeObserver.instances[0]?.trigger();
-
-		expect(onResize).toHaveBeenCalledTimes(1);
-	});
-
-	it('does not create an observer when the target is null', async () => {
-		new SvelteResizeObserver(() => null, vi.fn());
-
-		expect(MockResizeObserver.instances).toHaveLength(0);
-	});
-
-	it('can rebind to a new node and disconnect on destroy', () => {
-		const first = document.createElement('div');
-		const second = document.createElement('div');
-		let current = first;
-
-		const resizeObserver = new SvelteResizeObserver(() => current, vi.fn());
-
-		expect(MockResizeObserver.instances).toHaveLength(1);
-		expect(MockResizeObserver.instances[0]?.observed).toEqual([first]);
-
-		current = second;
-		resizeObserver.refresh();
-
-		expect(MockResizeObserver.instances).toHaveLength(2);
-		expect(MockResizeObserver.instances[0]?.disconnected).toBe(true);
-		expect(MockResizeObserver.instances[1]?.observed).toEqual([second]);
-
-		resizeObserver.destroy();
-
-		expect(MockResizeObserver.instances[1]?.disconnected).toBe(true);
-	});
-});