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/manager.spec.ts

@@ -12,7 +12,9 @@ import { entries, plainTurn } from './event-script.ts'
 const S1 = 'fk-m1' as SessionId
 const S2 = 'fk-m2' as SessionId
 
-function summary(sessionId: SessionId, over: Partial<{ updatedAt: number; running: boolean; blank: boolean; parentSessionId: SessionId }> = {}) {
+type SummaryOver = Partial<{ updatedAt: number; running: boolean; blank: boolean; parentSessionId: SessionId }>
+
+function summary(sessionId: SessionId, over: SummaryOver = {}) {
   return { sessionId, updatedAt: 100, running: false, blank: false, ...over }
 }