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, 92 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Util/Platform.php b/crates/shirabe-php-rpc/php/guards/Composer/Util/Platform.php
new file mode 100644
index 00000000..2384723d
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Util/Platform.php
@@ -0,0 +1,92 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Util\Platform.
+// 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;
+
+class Platform
+{
+    public function __construct()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public static function getCwd(bool $allowEmpty = false): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getCwd');
+    }
+
+    public static function realpath(string $path): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'realpath');
+    }
+
+    public static function getEnv(string $name)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getEnv');
+    }
+
+    public static function putEnv(string $name, string $value): void
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'putEnv');
+    }
+
+    public static function clearEnv(string $name): void
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'clearEnv');
+    }
+
+    public static function expandPath(string $path): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'expandPath');
+    }
+
+    public static function getUserDirectory(): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getUserDirectory');
+    }
+
+    public static function isWindowsSubsystemForLinux(): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isWindowsSubsystemForLinux');
+    }
+
+    public static function isWindows(): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isWindows');
+    }
+
+    public static function isDocker(): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isDocker');
+    }
+
+    public static function strlen(string $str): int
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'strlen');
+    }
+
+    public static function isTty($fd = null): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isTty');
+    }
+
+    public static function isInputCompletionProcess(): bool
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'isInputCompletionProcess');
+    }
+
+    public static function workaroundFilesystemIssues(): void
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'workaroundFilesystemIssues');
+    }
+
+    public static function getDevNull(): string
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'getDevNull');
+    }
+}