fix(plugin): resolve review findings in the plugin activation flow

InstallationManager::execute now takes &self (the mock recorder moved
into a RefCell) and its callers hold only shared borrows: plugin
registration inside a batch re-enters the same manager handle through
Composer::getInstallationManager()->getInstallPath(), which panicked
on the RefCell re-borrow under the &mut shape — the same re-entrancy
the repository side already fixed, unreachable from the ported tests
because they call PluginInstaller::install directly like PHPUnit does.

The worker-side InstalledVersions mirror now matches the full tail of
FilesystemRepository::write: unconditional reload plus the
reflection-based selfDir/installedIsLocalDir restore. The previous
class_exists(false) guard rested on a lazy-load assumption that does
not hold in the worker (its real ClassLoader only knows the Composer
checkout's vendor dir, so a later lazy load would read the checkout's
installed.php, not the project's); the mirror is now skipped only when
the class is not autoloadable at all, i.e. no plugin runtime and hence
no observer code. Boot-time seeding stays TODO(plugin).

Also from the review: registered_plugins entries are removed only
after the deactivate/uninstall loop (PHP unsets last, and a throw must
leave the entry observable); extra.class keeps associative-array
values and fails loudly on non-strings instead of silently dropping
them; the two discarded write() results now propagate (they carry the
reload-push failure); register_package's allow-plugins skip message is
DEBUG like the addPlugin side; the loader-eviction divergence of
REGISTERED_LOADERS and the lossy UTF-8 spots carry searchable
markers; the test-only proxy downcast follows the __ naming rule; the
R-table dispatch clones the entity out instead of holding the table
borrow across the handler; the IO/PartialComposer stubs turn a
plugin-side `new NullIO()` into an explicit error instead of an
ArgumentCountError; and the empty() emulation covers float 0.0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/crates/shirabe-php-rpc/src/lib.rs b/crates/shirabe-php-rpc/src/lib.rs
index cfee5e4c..9c5dae55 100644
--- a/crates/shirabe-php-rpc/src/lib.rs
+++ b/crates/shirabe-php-rpc/src/lib.rs
@@ -508,9 +508,9 @@ fn rpc_call(
                 send_frame(&reply)?;
             }
             Frame::ReleaseRustHandle { .. } => {
-                // TODO(plugin): there is no persistent R table yet (script-event handles are
-                // scoped to a single dispatched call), so stub destructor notifications carry no
-                // state to clean up.
+                // TODO(plugin): R-table garbage collection is deferred — the shirabe crate
+                // keeps its entries alive for the worker's lifetime, and per-call script-event
+                // handles carry no state either, so the notification is dropped here.
                 continue;
             }
             Frame::EpochBump { .. } => {