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>

4 files changed, 110 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Advisory/AuditConfig.php b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/AuditConfig.php
new file mode 100644
index 00000000..d45d56ad
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/AuditConfig.php
@@ -0,0 +1,24 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Advisory\AuditConfig.
+// 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\Advisory;
+
+use Composer\Config;
+
+class AuditConfig
+{
+    public function __construct(bool $audit, string $auditFormat, string $auditAbandoned, bool $blockInsecure, bool $blockAbandoned, bool $ignoreUnreachable, array $ignoreListForAudit, array $ignoreListForBlocking, array $ignoreSeverityForAudit, array $ignoreSeverityForBlocking, array $ignoreAbandonedForAudit, array $ignoreAbandonedForBlocking)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public static function fromConfig(Config $config, bool $audit = true, string $auditFormat = Auditor::FORMAT_SUMMARY): self
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'fromConfig');
+    }
+}
diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Advisory/IgnoredSecurityAdvisory.php b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/IgnoredSecurityAdvisory.php
new file mode 100644
index 00000000..56d423bc
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/IgnoredSecurityAdvisory.php
@@ -0,0 +1,25 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Advisory\IgnoredSecurityAdvisory.
+// 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\Advisory;
+
+use Composer\Semver\Constraint\ConstraintInterface;
+use DateTimeImmutable;
+
+class IgnoredSecurityAdvisory extends SecurityAdvisory
+{
+    public function __construct(string $packageName, string $advisoryId, ConstraintInterface $affectedVersions, string $title, array $sources, DateTimeImmutable $reportedAt, ?string $cve = null, ?string $link = null, ?string $ignoreReason = null, ?string $severity = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function jsonSerialize()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'jsonSerialize');
+    }
+}
diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Advisory/PartialSecurityAdvisory.php b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/PartialSecurityAdvisory.php
new file mode 100644
index 00000000..04d3b121
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/PartialSecurityAdvisory.php
@@ -0,0 +1,31 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Advisory\PartialSecurityAdvisory.
+// 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\Advisory;
+
+use Composer\Semver\Constraint\ConstraintInterface;
+use Composer\Semver\VersionParser;
+use JsonSerializable;
+
+class PartialSecurityAdvisory implements JsonSerializable
+{
+    public static function create(string $packageName, array $data, VersionParser $parser): self
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'create');
+    }
+
+    public function __construct(string $packageName, string $advisoryId, ConstraintInterface $affectedVersions)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function jsonSerialize()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'jsonSerialize');
+    }
+}
diff --git a/crates/shirabe-php-rpc/php/guards/Composer/Advisory/SecurityAdvisory.php b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/SecurityAdvisory.php
new file mode 100644
index 00000000..69749f77
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/guards/Composer/Advisory/SecurityAdvisory.php
@@ -0,0 +1,30 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Guard for Composer\Advisory\SecurityAdvisory.
+// 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\Advisory;
+
+use Composer\Semver\Constraint\ConstraintInterface;
+use DateTimeImmutable;
+
+class SecurityAdvisory extends PartialSecurityAdvisory
+{
+    public function __construct(string $packageName, string $advisoryId, ConstraintInterface $affectedVersions, string $title, array $sources, DateTimeImmutable $reportedAt, ?string $cve = null, ?string $link = null, ?string $severity = null)
+    {
+        \ShirabeUnsupportedClass::fail(self::class, '__construct');
+    }
+
+    public function toIgnoredAdvisory(?string $ignoreReason): IgnoredSecurityAdvisory
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'toIgnoredAdvisory');
+    }
+
+    public function jsonSerialize()
+    {
+        \ShirabeUnsupportedClass::fail(self::class, 'jsonSerialize');
+    }
+}