integrate effectified services with Bus Effect-native API

- Plugin: use bus.subscribeAll() Stream + forkScoped instead of callback facade
- Vcs: use bus.subscribe() Stream + forkScoped instead of acquireRelease callback
- Status: use bus.publish() Effect directly instead of Effect.promise wrapper
- Rewrite Vcs test to use facade functions (shared memoMap ensures singleton Bus)
- Add Bus integration tests for subscribe cleanup and instance disposal

packages/opencode/test/fixture/instance.ts

@@ -1,5 +1,6 @@
 import { ConfigProvider, Layer, ManagedRuntime } from "effect"
 import { InstanceContext } from "../../src/effect/instance-context"
+import { memoMap } from "../../src/effect/run-service"
 import { Instance } from "../../src/project/instance"
 
 /** ConfigProvider that enables the experimental file watcher. */