[Xdebug Bridge] Correct error related to unresolved promises in bridge (#2422)

## Motivation for the change, related issues

Resolves the [problem
introduced](https://github.com/WordPress/wordpress-playground/pull/2411/files#r2229819528)
in #2411:

> The promise returned by `getPHPFile()` is never resolved and the PHP
source code never loads in devtools

Author: mho22

packages/php-wasm/xdebug-bridge/src/lib/start-bridge.ts

@@ -14,7 +14,7 @@ export type StartBridgeConfig = {
 	localRoot?: string;
 
 	phpInstance?: PHP;
-	getPHPFile?: (path: string) => Promise<string>;
+	getPHPFile?: (path: string) => string | Promise<string>;
 };
 
 export async function startBridge(config: StartBridgeConfig) {
@@ -58,21 +58,17 @@ export async function startBridge(config: StartBridgeConfig) {
 	}
 
 	const getPHPFile = config.phpInstance
-		? (path: string) =>
-				new Promise<string>(() =>
-					config.phpInstance!.readFileAsText(path)
-				)
+		? (path: string) => config.phpInstance!.readFileAsText(path)
 		: config.getPHPFile
 		? config.getPHPFile
-		: (path: string) =>
-				new Promise<string>(() => {
-					// Default implementation: read from filesystem
-					// Convert file:/// URLs to local paths
-					const localPath = path.startsWith('file://')
-						? path.replace('file://', '')
-						: path;
-					return readFileSync(localPath, 'utf-8');
-				});
+		: (path: string) => {
+				// Default implementation: read from filesystem
+				// Convert file:/// URLs to local paths
+				const localPath = path.startsWith('file://')
+					? path.replace('file://', '')
+					: path;
+				return readFileSync(localPath, 'utf-8');
+		  };
 
 	const phpFiles = getPhpFiles(phpRoot);
 	return new XdebugCDPBridge(dbgpSession, cdpServer, {

packages/php-wasm/xdebug-bridge/src/lib/xdebug-cdp-bridge.ts

@@ -28,7 +28,7 @@ export interface XdebugCDPBridgeConfig {
 	knownScriptUrls: string[];
 	remoteRoot?: string;
 	localRoot?: string;
-	getPHPFile(path: string): Promise<string>;
+	getPHPFile(path: string): string | Promise<string>;
 }
 
 export class XdebugCDPBridge {
@@ -45,7 +45,7 @@ export class XdebugCDPBridge {
 	private xdebugConnected = false;
 	private xdebugStatus = 'starting';
 	private initFileUri: string | null = null;
-	private readPHPFile: (path: string) => Promise<string>;
+	private readPHPFile: (path: string) => string | Promise<string>;
 	private remoteRoot: string;
 	private localRoot: string;