Fix PluginPackagerTest for removed isCommonGitIgnoredPath method

Update two failing tests that called the removed isCommonGitIgnoredPath()
method, which was eliminated in commit 6253871 when the packager was
refactored to use .gitattributes export-ignore patterns as the single
source of truth.

Changes:
- testBuiltAssetsNotIgnored: Now uses getExportIgnorePatterns() and
  shouldExcludePath() to verify assets/dist/ is included in packages
- testVendorDirectoriesIgnored: Now uses getExportIgnorePatterns() and
  shouldExcludePath() to verify vendor/ is excluded from packages
- Updated section comment to reflect the new .gitattributes approach

The tests verify the same critical behaviors as before:
- Built assets (assets/dist/) must NOT be excluded from packages
- Dev dependencies (vendor/) must be excluded from packages
- Similar directory names (vendor_custom/) must not be incorrectly matched

Author: paulgoodchild

tests/Unit/PluginPackagerTest.php

@@ -123,8 +123,8 @@ public function testWindowsPathNormalization() :void {
 	}
 
 	// =========================================================================
-	// isCommonGitIgnoredPath() - Critical path handling
-	// Only test the critical case that could break packages
+	// .gitattributes export-ignore - Critical path handling
+	// Verify export-ignore patterns correctly include/exclude critical paths
 	// =========================================================================
 
 	/**
@@ -133,13 +133,14 @@ public function testWindowsPathNormalization() :void {
 	 */
 	public function testBuiltAssetsNotIgnored() :void {
 		$packager = $this->createPackager();
+		$patterns = $this->invokePrivateMethod( $packager, 'getExportIgnorePatterns', [] );
 
 		$this->assertFalse(
-			$this->invokePrivateMethod( $packager, 'isCommonGitIgnoredPath', [ 'assets/dist/bundle.js' ] ),
+			$this->invokePrivateMethod( $packager, 'shouldExcludePath', [ 'assets/dist/bundle.js', $patterns ] ),
 			'assets/dist/ contains built JS/CSS - must be in package'
 		);
 		$this->assertFalse(
-			$this->invokePrivateMethod( $packager, 'isCommonGitIgnoredPath', [ 'assets/dist' ] )
+			$this->invokePrivateMethod( $packager, 'shouldExcludePath', [ 'assets/dist', $patterns ] )
 		);
 	}
 
@@ -148,15 +149,16 @@ public function testBuiltAssetsNotIgnored() :void {
 	 */
 	public function testVendorDirectoriesIgnored() :void {
 		$packager = $this->createPackager();
+		$patterns = $this->invokePrivateMethod( $packager, 'getExportIgnorePatterns', [] );
 
 		// Root vendor/ contains dev dependencies
 		$this->assertTrue(
-			$this->invokePrivateMethod( $packager, 'isCommonGitIgnoredPath', [ 'vendor/phpunit/phpunit.php' ] )
+			$this->invokePrivateMethod( $packager, 'shouldExcludePath', [ 'vendor/phpunit/phpunit.php', $patterns ] )
 		);
 
 		// But vendor_custom/ (if it existed) should not match
 		$this->assertFalse(
-			$this->invokePrivateMethod( $packager, 'isCommonGitIgnoredPath', [ 'vendor_custom/file.php' ] ),
+			$this->invokePrivateMethod( $packager, 'shouldExcludePath', [ 'vendor_custom/file.php', $patterns ] ),
 			'Prefix match must not catch similar directory names'
 		);
 	}