[meta] Add ESLint rule for Node.js type stripping compatibility (#2951)

## Motivation for the change, related issues

Node.js type stripping (`--experimental-strip-types`) fails on
TypeScript syntax with runtime semantics. This caused runtime errors
like:

```
SyntaxError [ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX]: TypeScript parameter property is not supported
```

## Implementation details

Added the existing `@typescript-eslint/parameter-properties` ESLint rule
to prevent TypeScript parameter properties that are unsupported by
Node.js type stripping.

- **Parameter properties** — `constructor(private foo: string)` →
explicit property + assignment

Fixed existing violations:
- `blueprints-v1-handler.ts`, `blueprints-v2-handler.ts`,
`website-page.ts`, `code-editor.tsx` — converted parameter properties to
explicit declarations

## Testing Instructions (or ideally a Blueprint)

```bash
npm run lint
```

Verify the rule catches new violations:
```typescript
// Should error
class Foo {
  constructor(private bar: string) {}
}
```

<!-- START COPILOT CODING AGENT SUFFIX -->



<details>

<summary>Original prompt</summary>

> Start a new PR to add an eslint rule – only allow TypeScript syntax
that's supported by Node.js type stripping (to prevent future errors
such as this):
> 
> Version number df6471b7770cee7792040577 copied to clipboard
> Use Ctrl+C to stop the server
> node:internal/modules/run_main:123
>     triggerUncaughtException(
>     ^
> 
>
file:///Users/mho/Work/projects/xdebug/wordpress-playground/packages/playground/blueprints/src/lib/v1/compile.ts:47
> export class InvalidBlueprintError extends Error {
> constructor(message: string, public readonly validationErrors?:
unknown) {
> ^^^^^^^^^^^^^^^^^^^^^^^^^^
>         super(message);
> 
> SyntaxError [ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX]: TypeScript parameter
property is n
> 40 references
> Copilot said: Let me search for more specific ESLint
> Let me search for more specific ESLint configuration files in the
repository:Based on my research into the WordPress Playground
repository, I can see that:
> 
> The repo already has a custom ESLint plugin at
packages/meta/src/eslint-plugin-playground-dev/ with one existing rule
(avoid-wordpress-builds-dependency)
> The root .eslintrc.json already has some Node.js type stripping
support with @typescript-eslint/consistent-type-imports rule enabled
> The error you referenced is about TypeScript parameter properties
(like public readonly validationErrors), which are not supported by
Node.js type stripping. A new ESLint rule should be added to prevent
this syntax.
> 
> I'll create a PR that adds an ESLint rule to disallow TypeScript
syntax that's unsupported by Node.js type stripping, specifically:
> 
> Parameter properties (constructor(public foo: string))
> Enums (which also aren't supported by type stripping)
> Namespaces


</details>



<!-- START COPILOT CODING AGENT TIPS -->
---

💡 You can make Copilot smarter by setting up custom instructions,
customizing its development environment and configuring Model Context
Protocol (MCP) servers. Learn more [Copilot coding agent
tips](https://gh.io/copilot-coding-agent-tips) in the docs.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: adamziel <205419+adamziel@users.noreply.github.com>

Author: Copilot

.eslintrc.json

@@ -78,7 +78,9 @@
 				"no-constant-condition": 0,
 				"playground-dev/avoid-wordpress-builds-dependency": "error",
 				// Node.js type stripping requires explicit type imports.
-				"@typescript-eslint/consistent-type-imports": "error"
+				"@typescript-eslint/consistent-type-imports": "error",
+				// Disallow TypeScript parameter properties unsupported by Node.js type stripping.
+				"@typescript-eslint/parameter-properties": "error"
 			}
 		},
 		{

packages/playground/client/src/blueprints-v1-handler.ts

@@ -11,7 +11,11 @@ import { collectPhpLogs, logger } from '@php-wasm/logger';
 import { consumeAPI } from '@php-wasm/universal';
 
 export class BlueprintsV1Handler {
-	constructor(private readonly options: StartPlaygroundOptions) {}
+	private readonly options: StartPlaygroundOptions;
+
+	constructor(options: StartPlaygroundOptions) {
+		this.options = options;
+	}
 
 	async bootPlayground(
 		iframe: HTMLIFrameElement,

packages/playground/client/src/blueprints-v2-handler.ts

@@ -4,7 +4,11 @@ import { collectPhpLogs, logger } from '@php-wasm/logger';
 import { consumeAPI } from '@php-wasm/universal';
 
 export class BlueprintsV2Handler {
-	constructor(private readonly options: StartPlaygroundOptions) {}
+	private readonly options: StartPlaygroundOptions;
+
+	constructor(options: StartPlaygroundOptions) {
+		this.options = options;
+	}
 
 	async bootPlayground(
 		iframe: HTMLIFrameElement,

packages/playground/website/playwright/website-page.ts

@@ -2,7 +2,11 @@ import type { Page } from '@playwright/test';
 import { expect } from '@playwright/test';
 
 export class WebsitePage {
-	constructor(public readonly page: Page) {}
+	public readonly page: Page;
+
+	constructor(page: Page) {
+		this.page = page;
+	}
 
 	// Wait for WordPress to load
 	async waitForNestedIframes(page = this.page) {

packages/playground/website/src/components/site-manager/site-file-browser/code-editor.tsx

@@ -124,7 +124,10 @@ const loadLanguageExtension = async (
 
 // Plugin to handle clicks below the content and move cursor to end of document
 class ClickBelowContentHandler implements PluginValue {
-	constructor(private view: EditorViewType) {
+	private view: EditorViewType;
+
+	constructor(view: EditorViewType) {
+		this.view = view;
 		this.handleClick = this.handleClick.bind(this);
 		this.view.dom.addEventListener('mousedown', this.handleClick);
 	}