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 {

packages/client/ui-slash/src/core/detect.ts

@@ -18,12 +18,12 @@ const WHITESPACE = /\s/u
  */
 function boundaryOk(draft: string, index: number, char: TriggerChar): boolean {
   if (index === 0) return true
-  const prev = draft[index - 1]!
+  const prev = draft.charAt(index - 1)
   if (WHITESPACE.test(prev)) return true
   if (WORD_CHAR.test(prev)) return false
   if (char === '/') {
     if (prev === '/') return false
-    if (prev === ':' && index >= 2 && !WHITESPACE.test(draft[index - 2]!)) return false
+    if (prev === ':' && index >= 2 && !WHITESPACE.test(draft.charAt(index - 2))) return false
   }
   return true
 }
@@ -47,7 +47,7 @@ function boundaryOk(draft: string, index: number, char: TriggerChar): boolean {
 export const detectTrigger: DetectTrigger = (draft, caret, guard) => {
   if (guard.tier === 'frozen') return null
   for (let i = caret - 1; i >= 0; i--) {
-    const ch = draft[i]!
+    const ch = draft.charAt(i)
     if (WHITESPACE.test(ch)) return null
     if (ch !== '/' && ch !== '@') continue
     if (guard.tier === 'claimed' && ch === '/') continue

packages/client/ui-slash/src/core/menu.ts

@@ -110,15 +110,13 @@ export const menuReduce: MenuReduce = (state, ev) => {
       if (!state.open) return state
       const pos = positions(state.groups)
       if (pos.length === 0) return state
-      const at = state.highlight
-        ? pos.findIndex(p => p.source === state.highlight!.source && p.index === state.highlight!.index)
-        : -1
-      const next = at < 0
-        ? (ev.dir === 1 ? pos[0]! : pos[pos.length - 1]!)
-        : pos[(at + ev.dir + pos.length) % pos.length]!
-      if (state.highlight && next.source === state.highlight.source && next.index === state.highlight.index) {
-        return state
-      }
+      const hl = state.highlight
+      const at = hl ? pos.findIndex(p => p.source === hl.source && p.index === hl.index) : -1
+      const next = pos[at < 0
+        ? (ev.dir === 1 ? 0 : pos.length - 1)
+        : (at + ev.dir + pos.length) % pos.length]
+      if (next === undefined) return state
+      if (hl && next.source === hl.source && next.index === hl.index) return state
       return { ...state, highlight: next }
     }
     case 'close':