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, 81 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Json/JsonFile.php b/crates/shirabe-php-rpc/php/guards/Composer/Json/JsonFile.php
new file mode 100644
index 00000000..f61af348
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Json/JsonFile.php
@@ -0,0 +1,81 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Json\JsonFile.
+// 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\Json;
+
+use Composer\Util\HttpDownloader;
+use Composer\IO\IOInterface;
+
+class JsonFile
+{
+    public const LAX_SCHEMA = 1;
+    public const STRICT_SCHEMA = 2;
+    public const AUTH_SCHEMA = 3;
+    public const LOCK_SCHEMA = 4;
+    public const JSON_UNESCAPED_SLASHES = 64;
+    public const JSON_PRETTY_PRINT = 128;
+    public const JSON_UNESCAPED_UNICODE = 256;
+    public const COMPOSER_SCHEMA_PATH = __DIR__ . '/../../../res/composer-schema.json';
+    public const LOCK_SCHEMA_PATH = __DIR__ . '/../../../res/composer-lock-schema.json';
+    public const INDENT_DEFAULT = '    ';
+
+    public function __construct(string $path, ?HttpDownloader $httpDownloader = null, ?IOInterface $io = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function getPath(): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getPath');
+    }
+
+    public function exists(): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'exists');
+    }
+
+    public function read()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'read');
+    }
+
+    public function write(array $hash, int $options = JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'write');
+    }
+
+    public function validateSchema(int $schema = self::STRICT_SCHEMA, ?string $schemaFile = null): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'validateSchema');
+    }
+
+    public static function validateJsonSchema(string $source, $data, int $schema, ?string $schemaFile = null): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'validateJsonSchema');
+    }
+
+    public static function encode($data, int $options = \JSON_UNESCAPED_SLASHES | \JSON_PRETTY_PRINT | \JSON_UNESCAPED_UNICODE, string $indent = self::INDENT_DEFAULT): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'encode');
+    }
+
+    public static function parseJson(?string $json, ?string $file = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'parseJson');
+    }
+
+    protected static function validateSyntax(string $json, ?string $file = null): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'validateSyntax');
+    }
+
+    public static function detectIndenting(?string $json): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'detectIndenting');
+    }
+}