fix: resolve state variable shadowing in command, plugin, and tool/registry

The cache→state rename caused inner InstanceState.get() results to
shadow the outer state handle, breaking type inference. Rename inner
bindings to `s` to match the convention used in the other files.

packages/opencode/src/command/index.ts

@@ -164,13 +164,13 @@ export namespace Command {
       const state = yield* InstanceState.make<State>((ctx) => init(ctx))
 
       const get = Effect.fn("Command.get")(function* (name: string) {
-        const state = yield* InstanceState.get(state)
-        return state.commands[name]
+        const s = yield* InstanceState.get(state)
+        return s.commands[name]
       })
 
       const list = Effect.fn("Command.list")(function* () {
-        const state = yield* InstanceState.get(state)
-        return Object.values(state.commands)
+        const s = yield* InstanceState.get(state)
+        return Object.values(s.commands)
       })
 
       return Service.of({ get, list })