[chore] Replace npx with pnpx across the codebase (#5329)

## Summary
- Migrated all `npx` commands to `pnpx` to align with the pnpm ecosystem
- Updated all occurrences across the codebase for consistency

## Changes
- **Package.json scripts**: Updated test:browser, preinstall, and
collect-i18n scripts
- **GitHub Actions workflows**: Updated all workflow files that use npx
(test-ui, i18n, update-manager-types, etc.)
- **Documentation**: Updated browser_tests/README.md and
docs/extensions/development.md
- **Husky pre-commit hook**: Updated lint-staged and tsx commands
- **MCP configuration**: Updated .mcp.json to use pnpx

## Test Plan
- [ ] CI tests pass
- [ ] Local development commands work with pnpx
- [ ] GitHub Actions workflows execute successfully

🤖 Generated with Claude Code

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5329-chore-Replace-npx-with-pnpx-across-the-codebase-2646d73d36508127bd43d14b8364aeb1)
by [Unito](https://www.unito.io)

browser_tests/README.md

@@ -29,7 +29,7 @@ cp -r tools/devtools/* /path/to/your/ComfyUI/custom_nodes/ComfyUI_devtools/
 Ensure you have Node.js v20 or v22 installed. Then, set up the Chromium test driver:
 
 ```bash
-npx playwright install chromium --with-deps
+pnpm exec playwright install chromium --with-deps
 ```
 
 ### Environment Configuration
@@ -73,7 +73,7 @@ For tests that specifically need to test release functionality, see the example
 **Always use UI mode for development:**
 
 ```bash
-npx playwright test --ui
+pnpm exec playwright test --ui
 ```
 
 UI mode features:
@@ -89,8 +89,8 @@ UI mode features:
 For CI or headless testing:
 
 ```bash
-npx playwright test                    # Run all tests
-npx playwright test widget.spec.ts     # Run specific test file
+pnpm exec playwright test                    # Run all tests
+pnpm exec playwright test widget.spec.ts     # Run specific test file
 ```
 
 ### Local Development Config
@@ -386,7 +386,7 @@ export default defineConfig({
 Option 2 - Generate local baselines for comparison:
 
 ```bash
-npx playwright test --update-snapshots
+pnpm exec playwright test --update-snapshots
 ```
 
 ### Creating New Screenshot Baselines