chore(lint): clear the semantic .tsx backlog

Hand fixes for the findings --fix cannot touch, mirroring the fixes
already applied on the fe-docs feature branch (same file, same shape)
so its eventual rebase resolves cleanly:

- restore the return the no-confusing-void-expression autofix ate in
  useAbsentSnapshot (typed S | undefined; hook call kept for hook-order
  stability, undefined returned explicitly);
- re-type DOM queries the no-unnecessary-type-assertion autofix broke:
  getByRole<HTMLButtonElement>(...) generics instead of the removed
  as-casts (the eslint program and the client tsconfig aggregate
  disagree about these casts; the generic form satisfies both);
- justified eslint-disable for the deliberate legacy paths: keyCode 229
  IME-composition detection, execCommand clipboard fallbacks, lib.dom
  clipboard optionality, and the any-typed Reflect.get/this probes in
  test fakes;
- drop the dead react/no-danger directive (eslint-plugin-react is not
  loaded, so the rule never applied) keeping its shiki rationale;
- delete the tautological 'Z' comparison and the renameTarget null
  check already implied by renameBlocked;
- css-module non-null assertions replaced by type widening
  (Button className, TAG_CLASS Record) per the established pattern;
- misc: max-len comment wraps, void generic drop in the deferred test
  helper, unused type imports, floating selectWorkspace promises voided,
  member-delimiter newlines in inline type literals.

packages/client/ui-conversation/tests/chat-view.spec.tsx

@@ -7,7 +7,8 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { Profiler } from 'react'
 import { act, cleanup, fireEvent, render } from '@testing-library/react'
 import type {
-  AssistantMessageNode, ConversationNode, ConversationSnapshot, RunningToolCall, SessionId, SessionListState, ToolResultNode, UserMessageNode, WorkspaceListState,
+  AssistantMessageNode, ConversationNode, ConversationSnapshot, RunningToolCall, SessionId,
+  SessionListState, ToolResultNode, UserMessageNode, WorkspaceListState,
 } from '@deepseek-ai/dsh-client-runtime/client'
 import { bindSnapshotSelector } from '@deepseek-ai/dsh-client-web-react'
 import { createSnapshotStore, PendingWait } from '@deepseek-ai/dsh-client-runtime/client'
@@ -39,7 +40,7 @@ function makeSource(init?: Partial<ConversationSnapshot>) {
   let snap: ConversationSnapshot = { ...snapshotBase(), ...init }
   const subs = new Set<() => void>()
   return {
-    set(next: Partial<ConversationSnapshot>) {
+    set: (next: Partial<ConversationSnapshot>) => {
       snap = { ...snap, ...next }
       for (const fn of [...subs]) fn()
     },