chore: migrate tests from tests-ui/ to colocate with source files (#7811)

## Summary

Migrates all unit tests from `tests-ui/` to colocate with their source
files in `src/`, improving discoverability and maintainability.

## Changes

- **What**: Relocated all unit tests to be adjacent to the code they
test, following the `<source>.test.ts` naming convention
- **Config**: Updated `vitest.config.ts` to remove `tests-ui` include
pattern and `@tests-ui` alias
- **Docs**: Moved testing documentation to `docs/testing/` with updated
paths and patterns

## Review Focus

- Migration patterns documented in
`temp/plans/migrate-tests-ui-to-src.md`
- Tests use `@/` path aliases instead of relative imports
- Shared fixtures placed in `__fixtures__/` directories

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7811-chore-migrate-tests-from-tests-ui-to-colocate-with-source-files-2da6d73d36508147a4cce85365dee614)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>

tests-ui/tests/composables/graph/useTransformSettling.test.ts

@@ -1,171 +0,0 @@
-import { mount } from '@vue/test-utils'
-import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import { nextTick, ref } from 'vue'
-
-import { useTransformSettling } from '@/renderer/core/layout/transform/useTransformSettling'
-
-describe('useTransformSettling', () => {
-  let element: HTMLDivElement
-
-  beforeEach(() => {
-    vi.useFakeTimers()
-    element = document.createElement('div')
-    document.body.appendChild(element)
-  })
-
-  afterEach(() => {
-    vi.useRealTimers()
-    document.body.removeChild(element)
-  })
-
-  it('should track wheel events and settle after delay', async () => {
-    const { isTransforming } = useTransformSettling(element, {
-      settleDelay: 200
-    })
-
-    // Initially not transforming
-    expect(isTransforming.value).toBe(false)
-
-    // Dispatch wheel event
-    element.dispatchEvent(new WheelEvent('wheel', { bubbles: true }))
-    await nextTick()
-
-    // Should be transforming
-    expect(isTransforming.value).toBe(true)
-
-    // Advance time but not past settle delay
-    vi.advanceTimersByTime(100)
-    expect(isTransforming.value).toBe(true)
-
-    // Advance past settle delay
-    vi.advanceTimersByTime(150)
-    expect(isTransforming.value).toBe(false)
-  })
-
-  it('should reset settle timer on subsequent wheel events', async () => {
-    const { isTransforming } = useTransformSettling(element, {
-      settleDelay: 300
-    })
-
-    // First wheel event
-    element.dispatchEvent(new WheelEvent('wheel', { bubbles: true }))
-    await nextTick()
-    expect(isTransforming.value).toBe(true)
-
-    // Advance time partially
-    vi.advanceTimersByTime(200)
-    expect(isTransforming.value).toBe(true)
-
-    // Another wheel event should reset the timer
-    element.dispatchEvent(new WheelEvent('wheel', { bubbles: true }))
-    await nextTick()
-
-    // Advance 200ms more - should still be transforming
-    vi.advanceTimersByTime(200)
-    expect(isTransforming.value).toBe(true)
-
-    // Need another 100ms to settle (300ms total from last event)
-    vi.advanceTimersByTime(100)
-    expect(isTransforming.value).toBe(false)
-  })
-
-  it('should not track pan events', async () => {
-    const { isTransforming } = useTransformSettling(element)
-
-    // Pointer events should not trigger transform
-    element.dispatchEvent(new PointerEvent('pointerdown', { bubbles: true }))
-    element.dispatchEvent(new PointerEvent('pointermove', { bubbles: true }))
-    await nextTick()
-
-    expect(isTransforming.value).toBe(false)
-  })
-
-  it('should work with ref target', async () => {
-    const targetRef = ref<HTMLElement | null>(null)
-    const { isTransforming } = useTransformSettling(targetRef, {
-      settleDelay: 200
-    })
-
-    // No target yet
-    expect(isTransforming.value).toBe(false)
-
-    // Set target
-    targetRef.value = element
-    await nextTick()
-
-    // Now events should work
-    element.dispatchEvent(new WheelEvent('wheel', { bubbles: true }))
-    await nextTick()
-    expect(isTransforming.value).toBe(true)
-
-    vi.advanceTimersByTime(200)
-    expect(isTransforming.value).toBe(false)
-  })
-
-  it('should use capture phase for events', async () => {
-    const captureHandler = vi.fn()
-    const bubbleHandler = vi.fn()
-
-    // Add handlers to verify capture phase
-    element.addEventListener('wheel', captureHandler, true)
-    element.addEventListener('wheel', bubbleHandler, false)
-
-    const { isTransforming } = useTransformSettling(element)
-
-    // Create child element
-    const child = document.createElement('div')
-    element.appendChild(child)
-
-    // Dispatch event on child
-    child.dispatchEvent(new WheelEvent('wheel', { bubbles: true }))
-    await nextTick()
-
-    // Capture handler should be called before bubble handler
-    expect(captureHandler).toHaveBeenCalled()
-    expect(isTransforming.value).toBe(true)
-
-    element.removeEventListener('wheel', captureHandler, true)
-    element.removeEventListener('wheel', bubbleHandler, false)
-  })
-
-  it('should clean up event listeners when component unmounts', async () => {
-    const removeEventListenerSpy = vi.spyOn(element, 'removeEventListener')
-
-    // Create a test component
-    const TestComponent = {
-      setup() {
-        const { isTransforming } = useTransformSettling(element)
-        return { isTransforming }
-      },
-      template: '<div>{{ isTransforming }}</div>'
-    }
-
-    const wrapper = mount(TestComponent)
-    await nextTick()
-
-    // Unmount component
-    wrapper.unmount()
-
-    // Should have removed wheel event listener
-    expect(removeEventListenerSpy).toHaveBeenCalledWith(
-      'wheel',
-      expect.any(Function),
-      expect.objectContaining({ capture: true })
-    )
-  })
-
-  it('should use passive listeners when specified', async () => {
-    const addEventListenerSpy = vi.spyOn(element, 'addEventListener')
-
-    useTransformSettling(element, {
-      passive: true
-    })
-
-    // Check that passive option was used for wheel event
-    expect(addEventListenerSpy).toHaveBeenCalledWith(
-      'wheel',
-      expect.any(Function),
-      expect.objectContaining({ passive: true, capture: true })
-    )
-  })
-})