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>

src/utils/searchAndReplace.test.ts

@@ -0,0 +1,86 @@
+import { describe, expect, it } from 'vitest'
+
+import { LGraph } from '@/lib/litegraph/src/litegraph'
+import type { LGraphNode } from '@/lib/litegraph/src/litegraph'
+import { applyTextReplacements } from '@/utils/searchAndReplace'
+
+describe('applyTextReplacements', () => {
+  // Test specifically the filename sanitization part
+  describe('filename sanitization', () => {
+    it('should replace invalid filename characters with underscores', () => {
+      // Mock the minimal app structure needed
+      const mockNodes = [
+        {
+          title: 'TestNode',
+          widgets: [
+            {
+              name: 'testWidget',
+              value:
+                'file/name?with<invalid>chars\\:*|"control\x00chars\x1F\x7F'
+            }
+          ]
+        } as LGraphNode
+      ]
+
+      const mockGraph = new LGraph()
+      for (const node of mockNodes) {
+        mockGraph.add(node)
+      }
+      const result = applyTextReplacements(mockGraph, '%TestNode.testWidget%')
+
+      // The expected result should have all invalid characters replaced with underscores
+      expect(result).toBe('file_name_with_invalid_chars_____control_chars__')
+    })
+
+    it('should handle various invalid filename characters individually', () => {
+      const testCases = [
+        { input: '/', expected: '_' },
+        { input: '?', expected: '_' },
+        { input: '<', expected: '_' },
+        { input: '>', expected: '_' },
+        { input: '\\', expected: '_' },
+        { input: ':', expected: '_' },
+        { input: '*', expected: '_' },
+        { input: '|', expected: '_' },
+        { input: '"', expected: '_' },
+        { input: '\x00', expected: '_' }, // NULL character
+        { input: '\x1F', expected: '_' }, // Unit separator
+        { input: '\x7F', expected: '_' } // Delete character
+      ]
+
+      for (const { input, expected } of testCases) {
+        const mockNodes = [
+          {
+            title: 'TestNode',
+            widgets: [{ name: 'testWidget', value: input }]
+          } as LGraphNode
+        ]
+
+        const mockGraph = new LGraph()
+        for (const node of mockNodes) {
+          mockGraph.add(node)
+        }
+        const result = applyTextReplacements(mockGraph, '%TestNode.testWidget%')
+        expect(result).toBe(expected)
+      }
+    })
+
+    it('should not modify valid filename characters', () => {
+      const validChars = 'abcABC123.-_ '
+
+      const mockNodes = [
+        {
+          title: 'TestNode',
+          widgets: [{ name: 'testWidget', value: validChars }]
+        } as LGraphNode
+      ]
+
+      const mockGraph = new LGraph()
+      for (const node of mockNodes) {
+        mockGraph.add(node)
+      }
+      const result = applyTextReplacements(mockGraph, '%TestNode.testWidget%')
+      expect(result).toBe(validChars)
+    })
+  })
+})