Revert to only scanning .php files and update test to pass version explicitly

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

features/checksum-plugin.feature

@@ -215,7 +215,7 @@ Feature: Validate checksums for WordPress plugins
     When I run `mv wp-content/plugins/duplicate-post/duplicate-post.php wp-content/plugins/duplicate-post/duplicate-post.php.renamed`
     Then STDERR should be empty
 
-    When I try `wp plugin verify-checksums duplicate-post --format=json`
+    When I try `wp plugin verify-checksums duplicate-post --version=3.2.1 --format=json`
     Then STDOUT should contain:
       """
       "plugin_name":"duplicate-post","file":"duplicate-post.php.renamed","message":"File was added"

src/Checksum_Plugin_Command.php

@@ -253,15 +253,8 @@ private function detect_version_from_directory( $plugin_dir ) {
 		}
 
 		// Try scanning PHP files for Version header using WordPress's get_file_data()
-		// Include both .php files and renamed .php.* files (e.g., .php.bak, .php.renamed)
-		$php_files = glob( $plugin_path . '/*.php' );
-		$renamed_files = glob( $plugin_path . '/*.php.*' );
-		$files = array_merge(
-			is_array( $php_files ) ? $php_files : array(),
-			is_array( $renamed_files ) ? $renamed_files : array()
-		);
-
-		if ( ! empty( $files ) ) {
+		$files = glob( $plugin_path . '/*.php' );
+		if ( is_array( $files ) && ! empty( $files ) ) {
 			foreach ( $files as $file ) {
 				if ( is_readable( $file ) ) {
 					$file_data = get_file_data(
@@ -274,6 +267,7 @@ private function detect_version_from_directory( $plugin_dir ) {
 				}
 			}
 		}
+		// If glob() failed (returns false), version will just not be detected from PHP files
 
 		return false;
 	}