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/platform/cloud/subscription/composables/useSubscriptionActions.test.ts

@@ -1,109 +0,0 @@
-import { beforeEach, describe, expect, it, vi } from 'vitest'
-
-import { useSubscriptionActions } from '@/platform/cloud/subscription/composables/useSubscriptionActions'
-
-// Mock dependencies
-const mockFetchBalance = vi.fn()
-const mockFetchStatus = vi.fn()
-const mockShowTopUpCreditsDialog = vi.fn()
-const mockExecute = vi.fn()
-
-vi.mock('@/composables/auth/useFirebaseAuthActions', () => ({
-  useFirebaseAuthActions: () => ({
-    fetchBalance: mockFetchBalance
-  })
-}))
-
-vi.mock('@/platform/cloud/subscription/composables/useSubscription', () => ({
-  useSubscription: () => ({
-    fetchStatus: mockFetchStatus
-  })
-}))
-
-vi.mock('@/services/dialogService', () => ({
-  useDialogService: () => ({
-    showTopUpCreditsDialog: mockShowTopUpCreditsDialog
-  })
-}))
-
-vi.mock('@/stores/commandStore', () => ({
-  useCommandStore: () => ({
-    execute: mockExecute
-  })
-}))
-
-// Mock window.open
-const mockOpen = vi.fn()
-Object.defineProperty(window, 'open', {
-  writable: true,
-  value: mockOpen
-})
-
-describe('useSubscriptionActions', () => {
-  beforeEach(() => {
-    vi.clearAllMocks()
-  })
-
-  describe('handleAddApiCredits', () => {
-    it('should call showTopUpCreditsDialog', () => {
-      const { handleAddApiCredits } = useSubscriptionActions()
-      handleAddApiCredits()
-      expect(mockShowTopUpCreditsDialog).toHaveBeenCalledOnce()
-    })
-  })
-
-  describe('handleMessageSupport', () => {
-    it('should execute support command and manage loading state', async () => {
-      const { handleMessageSupport, isLoadingSupport } =
-        useSubscriptionActions()
-
-      expect(isLoadingSupport.value).toBe(false)
-
-      const promise = handleMessageSupport()
-      expect(isLoadingSupport.value).toBe(true)
-
-      await promise
-      expect(mockExecute).toHaveBeenCalledWith('Comfy.ContactSupport')
-      expect(isLoadingSupport.value).toBe(false)
-    })
-
-    it('should handle errors gracefully', async () => {
-      mockExecute.mockRejectedValueOnce(new Error('Command failed'))
-      const { handleMessageSupport, isLoadingSupport } =
-        useSubscriptionActions()
-
-      await handleMessageSupport()
-      expect(isLoadingSupport.value).toBe(false)
-    })
-  })
-
-  describe('handleRefresh', () => {
-    it('should call both fetchBalance and fetchStatus', async () => {
-      const { handleRefresh } = useSubscriptionActions()
-      await handleRefresh()
-
-      expect(mockFetchBalance).toHaveBeenCalledOnce()
-      expect(mockFetchStatus).toHaveBeenCalledOnce()
-    })
-
-    it('should handle errors gracefully', async () => {
-      mockFetchBalance.mockRejectedValueOnce(new Error('Fetch failed'))
-      const { handleRefresh } = useSubscriptionActions()
-
-      // Should not throw
-      await expect(handleRefresh()).resolves.toBeUndefined()
-    })
-  })
-
-  describe('handleLearnMoreClick', () => {
-    it('should open learn more URL', () => {
-      const { handleLearnMoreClick } = useSubscriptionActions()
-      handleLearnMoreClick()
-
-      expect(mockOpen).toHaveBeenCalledWith(
-        'https://docs.comfy.org/get_started/cloud',
-        '_blank'
-      )
-    })
-  })
-})