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, 110 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Cache.php b/crates/shirabe-php-rpc/php/guards/Composer/Cache.php
new file mode 100644
index 00000000..286b262c
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Cache.php
@@ -0,0 +1,110 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Cache.
+// 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;
+
+use Composer\IO\IOInterface;
+use Composer\Util\Filesystem;
+
+class Cache
+{
+    public function __construct(IOInterface $io, string $cacheDir, string $allowlist = 'a-z0-9._', ?Filesystem $filesystem = null, bool $readOnly = false)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function setReadOnly(bool $readOnly)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'setReadOnly');
+    }
+
+    public function isReadOnly()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isReadOnly');
+    }
+
+    public static function isUsable(string $path)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isUsable');
+    }
+
+    public function isEnabled()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isEnabled');
+    }
+
+    public function getRoot()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getRoot');
+    }
+
+    public function read(string $file)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'read');
+    }
+
+    public function write(string $file, string $contents)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'write');
+    }
+
+    public function copyFrom(string $file, string $source)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'copyFrom');
+    }
+
+    public function copyTo(string $file, string $target)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'copyTo');
+    }
+
+    public function gcIsNecessary()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'gcIsNecessary');
+    }
+
+    public function remove(string $file)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'remove');
+    }
+
+    public function clear()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'clear');
+    }
+
+    public function getAge(string $file)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getAge');
+    }
+
+    public function gc(int $ttl, int $maxSize)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'gc');
+    }
+
+    public function gcVcsCache(int $ttl): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'gcVcsCache');
+    }
+
+    public function sha1(string $file)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'sha1');
+    }
+
+    public function sha256(string $file)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'sha256');
+    }
+
+    protected function getFinder()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getFinder');
+    }
+}