feat(web): a prose mention of a produced file opens it

The chatFileMentions service (provided by ui-deliverables beside its
turn-tail entry, reached via ctx.get) resolves inline-code tokens in the
closing message against the turn's produced locations: exact path or
unique basename links, ambiguity and unknowns stay inert. MarkdownText
gains the optional fileMentions seam — settled renders only, never
inside anchors.

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

@@ -335,7 +335,8 @@ function StreamingTail({ useSession, t }: {
  * render through the declared keyed hole's renderSlot share).
  */
 export function ChatView({
-  useSession, useSessions, useStore, renderSlot, renderSlotChain, sessionId, openFile, loadOlder, inspectCall, chatScroll, forkAt, t,
+  useSession, useSessions, useStore, renderSlot, renderSlotChain, sessionId, openFile, loadOlder, inspectCall, chatScroll, forkAt,
+  fileMentions, t,
 }: ChatViewSlotProps) {
   const nodes = useSession(s => s.nodes)
   const turnTimings = useSession(s => s.turnTimings)
@@ -603,6 +604,7 @@ export function ChatView({
           turnTail={actionSeqs.has(node.seq)
             ? { renderSlotChain, owner: { nodes, seq: node.seq, openFile } }
             : undefined}
+          fileMentions={actionSeqs.has(node.seq) ? fileMentions : undefined}
           t={t}
         />
       )