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, 6 insertions, 0 deletions

diff --git a/crates/shirabe/tests/installer_test.rs b/crates/shirabe/tests/installer_test.rs
index d0b60ba8..1a8b7ccc 100644
--- a/crates/shirabe/tests/installer_test.rs
+++ b/crates/shirabe/tests/installer_test.rs
@@ -188,6 +188,12 @@ impl EventDispatcherInterface for StubEventDispatcher {
         Ok(0)
     }
     fn add_listener(&mut self, _event_name: &str, _listener: Callable, _priority: i64) {}
+    fn add_subscriber(
+        &mut self,
+        _subscriber: &dyn shirabe::event_dispatcher::EventSubscriberInterface,
+    ) -> anyhow::Result<()> {
+        Ok(())
+    }
     fn has_event_listeners(&mut self, _event: &dyn EventInterface) -> bool {
         false
     }