feat(plugin): dispatch plugin event subscribers through the RPC worker

Wires the addPlugin subscriber branch end to end: EventSubscriberInterface
and Capable become fallible and dyn-compatible (their sole implementor is
the PHP plugin proxy, which answers getSubscribedEvents over RPC), listeners
register as Callable::PhpMethod and are invoked with a per-call event handle,
and the R table now drops entries when a child-side stub destructs. The R
table keeps its IndexMap with monotonically increasing handles, so released
handles are never reused and no generation counter is needed.

Upstream has no subscriber-plugin test, so the path is covered by a
Shirabe-owned fixture exercising all three getSubscribedEvents shapes.

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

1 files changed, 5 insertions, 5 deletions

diff --git a/crates/shirabe/src/plugin/plugin_interface.rs b/crates/shirabe/src/plugin/plugin_interface.rs
index 989329ea..586fb43b 100644
--- a/crates/shirabe/src/plugin/plugin_interface.rs
+++ b/crates/shirabe/src/plugin/plugin_interface.rs
@@ -1,6 +1,7 @@
 //! ref: composer/src/Composer/Plugin/PluginInterface.php
 
 use crate::composer::ComposerHandle;
+use crate::event_dispatcher::EventSubscriberInterface;
 use crate::io::IOInterface;
 use crate::plugin::Capable;
 
@@ -31,11 +32,10 @@ pub trait PluginInterface: std::fmt::Debug {
     /// the name PHP would report.
     fn get_class_name(&self) -> String;
 
-    // TODO(plugin): PHP-side `instanceof` checks for EventSubscriberInterface / Capable.
-    // EventSubscriberInterface is not dyn-compatible (its only method is associated, not
-    // a `&self` method), so we expose a boolean predicate instead.
-    fn is_event_subscriber_interface(&self) -> bool {
-        false
+    // PHP-side `instanceof EventSubscriberInterface` / `instanceof Capable` checks map to
+    // these downcast accessors.
+    fn as_event_subscriber(&self) -> Option<&dyn EventSubscriberInterface> {
+        None
     }
 
     fn as_capable(&self) -> Option<&dyn Capable> {