feat(plugin): guard Rust-owned classes the worker has no proxy for

The worker's autoloader fell through to the real Composer source for every
Rust-owned FQCN without a proxy stub, so plugin code doing `new Filesystem()`
or subclassing `LibraryInstaller` silently ran on a second instance the Rust
side never sees. An unimplemented part of the plugin API has to fail with an
explicit error naming it, not quietly work on a disconnected copy.

The stub generator now emits a guard class for each of those FQCNs: the real
declaration, hierarchy and constants, with every constructor and method
raising an explicit error. References satisfied by the declaration alone
(`instanceof`, `X::class`, `Link::TYPE_REQUIRE`) keep working. Two FQCNs stay
resolvable to the real class, each listed with the worker-side mechanism that
makes a natively constructed instance correct.

The error had nowhere to go: `Installer::run` dropped the `Result` of both
`dispatch_script` calls, so an exception from a listener ended in exit 0.
Both propagate now, the way the exception does upstream.

Three real-plugin E2E comparisons stop at a guard and are ignored, each
naming the class it needs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Util/RemoteFilesystem.php b/crates/shirabe-php-rpc/php/guards/Composer/Util/RemoteFilesystem.php
new file mode 100644
index 00000000..3cf20768
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Util/RemoteFilesystem.php
@@ -0,0 +1,85 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Util\RemoteFilesystem.
+// The Rust side owns this class and the worker has no proxy for it, so this
+// declaration shadows the real one: the constants and the hierarchy stay, while
+// constructing it or calling anything on it raises an explicit error.
+
+namespace Composer\Util;
+
+use Composer\Config;
+use Composer\IO\IOInterface;
+
+class RemoteFilesystem
+{
+    public function __construct(IOInterface $io, Config $config, array $options = [], bool $disableTls = false, ?AuthHelper $authHelper = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function copy(string $originUrl, string $fileUrl, string $fileName, bool $progress = true, array $options = [])
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'copy');
+    }
+
+    public function getContents(string $originUrl, string $fileUrl, bool $progress = true, array $options = [])
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getContents');
+    }
+
+    public function getOptions()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getOptions');
+    }
+
+    public function setOptions(array $options)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'setOptions');
+    }
+
+    public function isTlsDisabled()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isTlsDisabled');
+    }
+
+    public function getLastHeaders()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getLastHeaders');
+    }
+
+    public static function findStatusCode(array $headers)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'findStatusCode');
+    }
+
+    public function findStatusMessage(array $headers)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'findStatusMessage');
+    }
+
+    protected function get(string $originUrl, string $fileUrl, array $additionalOptions = [], ?string $fileName = null, bool $progress = true)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'get');
+    }
+
+    protected function getRemoteContents(string $originUrl, string $fileUrl, $context, ?array &$responseHeaders = null, ?int $maxFileSize = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getRemoteContents');
+    }
+
+    protected function callbackGet(int $notificationCode, int $severity, ?string $message, int $messageCode, int $bytesTransferred, int $bytesMax)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'callbackGet');
+    }
+
+    protected function promptAuthAndRetry($httpStatus, ?string $reason = null, array $headers = [])
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'promptAuthAndRetry');
+    }
+
+    protected function getOptionsForUrl(string $originUrl, array $additionalOptions)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getOptionsForUrl');
+    }
+}