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/ui-slash/src/client/controller.ts

@@ -211,7 +211,10 @@ export class SlashController {
     return undefined
   }
 
-  /** Drop the menu group of a disposed source (root registry change notification). */
+  /**
+   * Drop the menu group of a disposed source (root registry change notification).
+   * @param source - the source whose registration was disposed.
+   */
   sourceRemoved(source: SlashSource): void {
     const state = this.menu.getSnapshot()
     if (state.open && state.hit !== null && state.hit.trigger === source.trigger) {

packages/client/ui-slash/src/client/index.ts

@@ -52,7 +52,7 @@ export function apply(ctx: ClientContext): void {
       inject: (sessionId): MenuViewInjected => {
         // Session-scoped slot: resolve this session's controller (the slot
         // frame hands ids, not ctx — the registered id→ctx interchange).
-        const actx = sessions.scope(sessionId as Parameters<typeof sessions.scope>[0])
+        const actx = sessions.scope(sessionId)
         if (actx === undefined) throw new Error(`ui-slash: session "${String(sessionId)}" resolved no scope`)
         const controller = slash.sessionOf(actx)
         return {