Add an action seat to human messages (conversation.chat.user-actions)

[HughWise]

TL;DR

Replies already expose conversation.chat.assistant-actions, so a plugin can add an entry to the icon row under an assistant message. The icon row under a human message exposes no slot at all, so a plugin cannot add anything there. This proposes one new client slot with the same shape as the existing one: conversation.chat.user-actions.

Current state

• conversation.chat.assistant-actions — list, session scope, owner { messageId }; rendered inline in the icon row under the Turn-closing reply, beside copy, like/dislike, branch, usage and the clock.
• The icon row under a user bubble (MessageIconActions) renders only the built-in copy control. There is no seat, so quote, export, send-to-MCP or translate style actions cannot live in that row.

Proposal

Change	Detail
New slot	'conversation.chat.user-actions' — kind: 'list', scope: 'session'
Owner props	MessageActionOwnerProps { messageId: MessageId; text: string }, shared by both strips (AssistantActionOwnerProps / UserActionOwnerProps are aliases)
Rendering	Inline in the same row, right after the built-in copy control
Steering rows	A separate SteeringMessageNodeView; a steering row has no durable message identity, so it must not receive the seat

text is the body the built-in copy control writes. It is new on the assistant owner as well: today a plugin that wants the reply body has to reconstruct it.

Rows without durable identity — pending submissions, echo rows, steering rows, interruption-frozen partials — render no contributions.

Left: the built-in copy control. Right: an entry contributed by a zero-build plugin into both strips. The plugin (4 files, no build step) is on the same branch: demo/user-actions.

Blast radius

• Additive only: no Session format change, no model-visible change, no new package.
• Regenerated client slot catalog, so cordis_inspect lists the new seat.
• Docs updated in the same change: docs/subsystems/slots.md (slot tree plus strip description) and the @deepseek-ai/dsh-client-ui-chat README, each with its Chinese pair.
• Tests: the ui-chat suite passes locally (974 tests); a case asserts that a contributed entry renders in the same row after copy, and that steering rows render none.

Alternative considered

Mounting a child slot on conversation.chat.node keyed by node kind would not be inline in the row, and it would force the row to hand down the messageId and text that the seat already carries.

Ask

Is this scope acceptable upstream? If it is, the change is a 16-file diff and I can provide a patch or a PR — I understand external PRs are not accepted at the moment, so posting here first.

Diff: master...feat/user-message-actions

[HughWise]

参考效果