Add Playwright composite action to reduce workflow duplication (#5754)

This PR introduces a reusable composite action for Playwright setup to
reduce duplication across workflows.

## Changes
- Created `.github/actions/setup-playwright/action.yml` composite action
that:
  - Detects or uses provided Playwright version
  - Caches Playwright browsers with intelligent cache keys
  - Installs browsers only when cache miss occurs
  - Installs OS dependencies when cache hit occurs
  
## Technical Details
- **Important:** The composite action requires `shell: bash` for all
`run` steps as per [GitHub Actions requirements for composite
actions](https://docs.github.com/en/actions/creating-actions/creating-a-composite-action#creating-an-action-metadata-file).
This is a mandatory field for composite actions, unlike regular workflow
steps.
- Updated workflow paths to account for repository checkout locations
(some workflows checkout to subdirectories like `ComfyUI_frontend/`)
- Uses conditional caching to avoid redundant browser installations

## Benefits
- Reduces code duplication across 6 workflow files
- Centralizes Playwright caching logic  
- Consistent browser setup across all workflows
- Easier maintenance and updates
- Faster CI runs through intelligent caching

## Affected Workflows
- `.github/workflows/test-ui.yaml` (2 uses)
- `.github/workflows/i18n-custom-nodes.yaml`
- `.github/workflows/i18n-node-defs.yaml`
- `.github/workflows/i18n.yaml`
- `.github/workflows/test-browser-exp.yaml`

---------

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

src/lib/litegraph/src/LGraphNode.ts

@@ -902,7 +902,7 @@ export class LGraphNode
 
     if (this.onSerialize?.(o))
       console.warn(
-        'node onSerialize shouldn\'t return anything, data should be stored in the object pass in the first parameter'
+        "node onSerialize shouldn't return anything, data should be stored in the object pass in the first parameter"
       )
 
     return o