cleanup(web): drop the unimplemented user-message edit control

The user bubble's IconActions row carried an edit button with no click
handler, no client mutation, and no host operation behind it, advertising
an affordance the product cannot honor. The row now renders clock / copy /
branch only for both user and assistant chrome, and MessageIconActions
loses the `edit` prop with the button.

The package README records the missing capability under Known Limitations,
the web aria goldens pin the row without the control, and the Agent Note
states what must exist before it comes back.

packages/client/ui-conversation/src/client/chat/MessageIconActions.tsx

@@ -1,10 +1,9 @@
 // Shared IconActions chrome for user and assistant messages: copy live,
-// branch wired through onBranch, date-aware clock,
-// optional edit stub.
+// branch wired through onBranch, date-aware clock.
 
 import { useCallback } from 'react'
 import {
-  IconBranchOutline16, IconCopyOutline16, IconEditOutline16, Tooltip,
+  IconBranchOutline16, IconCopyOutline16, Tooltip,
 } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { ChatViewSlotProps } from '../contract/slots.ts'
 import { formatMessageClock, writeClipboard } from './message-chrome.ts'
@@ -18,8 +17,6 @@ export interface MessageIconActionsProps {
   time: number
   /** Clock before icons (user) or after (assistant). */
   clock: 'start' | 'end'
-  /** When true, append the stub edit control (user bubble). */
-  edit?: boolean | undefined
   /** Fork the session at this message. */
   onBranch?: (() => void) | undefined
   /** Parent layout class composed onto the actions row. */
@@ -30,11 +27,11 @@ export interface MessageIconActionsProps {
 
 /**
  * Copy / branch (/ clock) IconActions row shared by user and assistant chrome.
- * @param props - Copy text, event time, clock side, optional edit, branch callback, className.
+ * @param props - Copy text, event time, clock side, branch callback, className.
  * @returns The actions row element.
  */
 export function MessageIconActions({
-  text, time, clock, edit, onBranch, className, t,
+  text, time, clock, onBranch, className, t,
 }: MessageIconActionsProps) {
   const day = useCalendarDay()
   const onCopy = useCallback(() => {
@@ -58,13 +55,6 @@ export function MessageIconActions({
           <IconBranchOutline16 />
         </button>
       </Tooltip>
-      {edit === true && (
-        <Tooltip label={t('edit')} side="bottom">
-          <button type="button" className={css.action} aria-label={t('edit')}>
-            <IconEditOutline16 />
-          </button>
-        </Tooltip>
-      )}
       {clock === 'end' ? clockEl : null}
     </div>
   )

packages/client/ui-conversation/src/client/chat/MessageItem.tsx

@@ -156,7 +156,6 @@ export const MessageItem = memo(function MessageItem({
             text={text}
             time={node.time}
             clock="start"
-            edit
             onBranch={onFork === undefined ? undefined : () => { onFork(node.seq) }}
             className={css.actions}
             t={t}