CLI: Show clear error for non-existent WordPress versions (#3065)

* Validate WordPress version against available versions in CLI site create

When a user specifies a non-existent WordPress version via --wp flag,
the command now fails early with a clear error listing available versions
instead of proceeding through all setup steps and failing with a generic
server startup error.

* Validate WordPress version before interactive prompts

Move the version availability check to the top of the handler so it
fails immediately when --wp is passed with a non-existent version,
instead of after the user fills in all interactive prompts.

* Validate and resolve WordPress version in CLI site create

When --wp flag specifies a non-existent version, show a clear error
listing available versions instead of failing with a generic server
error. Short versions like "6.7" are resolved to full versions like
"6.7.2" with a log message showing the resolution.

* Start spinner before version validation to fix silent output

picospinner requires the spinner to be running for fail/succeed to
render output. Start it with a "Checking WordPress version" message
before fetching available versions.

Author: gcsecsey

apps/cli/commands/site/create.ts

@@ -638,6 +638,55 @@ export const registerCommand = ( yargs: StudioArgv ) => {
 			let adminPassword = argv.adminPassword;
 			let adminEmail = argv.adminEmail;
 
+			// Validate and resolve the WordPress version against available versions before prompting
+			if ( wpVersion && wpVersion !== 'latest' && wpVersion !== 'nightly' ) {
+				try {
+					logger.reportStart( LoggerAction.VALIDATE, __( 'Checking WordPress version…' ) );
+					const availableVersions = await fetchWordPressVersions();
+					const matchedVersion = availableVersions.find(
+						( v ) => v.value === wpVersion || v.value.startsWith( wpVersion + '.' )
+					);
+					if ( ! matchedVersion ) {
+						const versionLabels = availableVersions
+							.filter( ( v ) => v.value !== 'latest' )
+							.map( ( v ) => v.label );
+						logger.reportError(
+							new LoggerError(
+								sprintf(
+									/* translators: %1$s: requested version, %2$s: list of available versions */
+									__( 'WordPress version "%1$s" is not available. Available versions: %2$s' ),
+									wpVersion,
+									versionLabels.join( ', ' )
+								)
+							)
+						);
+						return;
+					}
+					// Resolve short versions to full versions (e.g. "6.7" → "6.7.2")
+					if ( matchedVersion.value !== wpVersion ) {
+						logger.reportSuccess(
+							sprintf(
+								/* translators: %1$s: requested version, %2$s: resolved version */
+								__( 'WordPress version: %1$s → %2$s' ),
+								wpVersion,
+								matchedVersion.value
+							)
+						);
+					} else {
+						logger.reportSuccess(
+							sprintf(
+								/* translators: %s: WordPress version */
+								__( 'WordPress version: %s' ),
+								wpVersion
+							)
+						);
+					}
+					wpVersion = matchedVersion.value;
+				} catch {
+					// If we can't fetch versions (network issue), let it proceed and fail later
+				}
+			}
+
 			try {
 				if ( process.stdin.isTTY ) {
 					if ( ! siteName ) {