style: fix lint across client packages

eslint --fix autofixes plus manual repairs: max-len line splits
(fake-api handlers, notifier/slots JSDoc, spec signatures), charAt over
non-null-asserted indexing in slash detect/menu cores, Array.from for
code-point capping, typeof assertions for unbound-method in specs,
generic getByRole for the send-button cast, effect disposer void-wrap in
command register, and dropped unused type imports.

packages/client/runtime/tests/slots-service.spec.ts

@@ -104,10 +104,10 @@ function fakeSessions() {
     list: { getSnapshot: () => state, subscribe: () => () => undefined },
     provideInfo: (id: string) => (id === 'known'
       ? {
-          sessionId: id,
-          hooks: { session: { getSnapshot: () => undefined, subscribe: () => () => undefined } },
-          props: {},
-        }
+        sessionId: id,
+        hooks: { session: { getSnapshot: () => undefined, subscribe: () => () => undefined } },
+        props: {},
+      }
       : undefined),
   }
 }