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, 20 insertions, 0 deletions

diff --git a/crates/shirabe-php-rpc/build.rs b/crates/shirabe-php-rpc/build.rs
index 07a77a07..937d0bb2 100644
--- a/crates/shirabe-php-rpc/build.rs
+++ b/crates/shirabe-php-rpc/build.rs
@@ -79,6 +79,26 @@ fn main() {
     )
     .unwrap();
     println!("cargo::rustc-env=SHIRABE_COMPOSER_RUNTIME_BUNDLE_ID={bundle_id}");
+
+    write_guard_files(&manifest_dir.join("php/guards"), &out_dir);
+}
+
+/// Writes the initializer of `GUARD_FILES`: one `include_str!` per generated guard class. The
+/// list is built here rather than spelled out in the source because there is one guard for every
+/// Rust-owned class the worker has no proxy stub for.
+fn write_guard_files(guards: &Path, out_dir: &Path) {
+    println!("cargo::rerun-if-changed={}", guards.display());
+
+    let mut code = String::from("&[\n");
+    for file in find_files(guards) {
+        code += &format!(
+            "    ({:?}, include_str!({:?})),\n",
+            relative_path(guards, &file),
+            file.to_str().unwrap()
+        );
+    }
+    code += "]\n";
+    std::fs::write(out_dir.join("guard-files.rs"), code).unwrap();
 }
 
 /// Every file the bundle holds, in the order `Compiler::compile` adds them.