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/litegraph/utils/textUtils.test.ts

@@ -1,82 +0,0 @@
-import { describe, expect, it, vi } from 'vitest'
-
-import { truncateText } from '@/lib/litegraph/src/litegraph'
-
-describe('truncateText', () => {
-  const createMockContext = (charWidth: number = 10) => {
-    return {
-      measureText: vi.fn((text: string) => ({ width: text.length * charWidth }))
-    } as unknown as CanvasRenderingContext2D
-  }
-
-  it('should return original text if it fits within maxWidth', () => {
-    const ctx = createMockContext()
-    const result = truncateText(ctx, 'Short', 100)
-    expect(result).toBe('Short')
-  })
-
-  it('should return original text if maxWidth is 0 or negative', () => {
-    const ctx = createMockContext()
-    expect(truncateText(ctx, 'Text', 0)).toBe('Text')
-    expect(truncateText(ctx, 'Text', -10)).toBe('Text')
-  })
-
-  it('should truncate text and add ellipsis when text is too long', () => {
-    const ctx = createMockContext(10) // 10 pixels per character
-    const result = truncateText(ctx, 'This is a very long text', 100)
-    // 100px total, "..." takes 30px, leaving 70px for text (7 chars)
-    expect(result).toBe('This is...')
-  })
-
-  it('should use custom ellipsis when provided', () => {
-    const ctx = createMockContext(10)
-    const result = truncateText(ctx, 'This is a very long text', 100, '…')
-    // 100px total, "…" takes 10px, leaving 90px for text (9 chars)
-    expect(result).toBe('This is a…')
-  })
-
-  it('should return only ellipsis if available width is too small', () => {
-    const ctx = createMockContext(10)
-    const result = truncateText(ctx, 'Text', 20) // Only room for 2 chars, but "..." needs 3
-    expect(result).toBe('...')
-  })
-
-  it('should handle empty text', () => {
-    const ctx = createMockContext()
-    const result = truncateText(ctx, '', 100)
-    expect(result).toBe('')
-  })
-
-  it('should use binary search efficiently', () => {
-    const ctx = createMockContext(10)
-    const longText = 'A'.repeat(100) // 100 characters
-
-    const result = truncateText(ctx, longText, 200) // Room for 20 chars total
-    expect(result).toBe(`${'A'.repeat(17)}...`) // 17 chars + "..." = 20 chars = 200px
-
-    // Verify binary search efficiency - should not measure every possible substring
-    // Binary search for 100 chars should take around log2(100) ≈ 7 iterations
-    // Plus a few extra calls for measuring the full text and ellipsis
-    const callCount = (ctx.measureText as any).mock.calls.length
-    expect(callCount).toBeLessThan(20)
-    expect(callCount).toBeGreaterThan(5)
-  })
-
-  it('should handle unicode characters correctly', () => {
-    const ctx = createMockContext(10)
-    const result = truncateText(ctx, 'Hello 👋 World', 80)
-    // Assuming each char (including emoji) is 10px, total is 130px
-    // 80px total, "..." takes 30px, leaving 50px for text (5 chars)
-    expect(result).toBe('Hello...')
-  })
-
-  it('should handle exact boundary cases', () => {
-    const ctx = createMockContext(10)
-
-    // Text exactly fits
-    expect(truncateText(ctx, 'Exact', 50)).toBe('Exact') // 5 chars = 50px
-
-    // Text is exactly 1 pixel too long
-    expect(truncateText(ctx, 'Exact!', 50)).toBe('Ex...') // 6 chars = 60px, truncated
-  })
-})