feat(feedback): add the Web surface for message feedback

Consume the durable message-feedback sidecar from #2217 in the browser:
per-message Like/Dislike with an optional note, contributed through a
declared assistant-actions slot.

- carry MessageId on finalized AssistantMessageNode so a target is nameable
- declare conversation.chat.assistant-actions and render it in the
  IconActions row between copy and branch
- hold one FeedbackController per Session with per-item ifVersion CAS,
  reconciling a version-conflict from the reply's authoritative item
- mount messageFeedbackRemote alongside goalsRemote

tsconfig.base.json

@@ -175,6 +175,7 @@
       "@deepseek-ai/dsh-client-ui-command": ["./packages/client/ui-command/src"],
       "@deepseek-ai/dsh-client-ui-model": ["./packages/client/ui-model/src"],
       "@deepseek-ai/dsh-client-ui-goal": ["./packages/client/ui-goal/src"],
+      "@deepseek-ai/dsh-client-ui-feedback": ["./packages/client/ui-feedback/src"],
       "@deepseek-ai/dsh-client-ui-agent-preset": ["./packages/client/ui-agent-preset/src"],
       "@deepseek-ai/dsh-client-ui-permission": ["./packages/client/ui-permission/src"],
       "@deepseek-ai/dsh-client-ui-skill": ["./packages/client/ui-skill/src"],