web-ui: surface mid-turn agent posts in the live dock and pre-refresh timeline

[irisfeng]

Problem

When the agent posts a message to the conversation mid-turn (the surface tool's action: "post"), that text is effectively invisible in the web UI at the moment it is sent:

• While the turn streams, run activity carries no text entries, and the live dock has no summary for the surface tool — it shows a generic "Working" line, so the posted text is nowhere in the transcript.
• After the turn ends, the post sits inside the collapsed N tool calls fold. Only the settled transcript rebuild (which lifts posts into assistant content bubbles) makes the text visible; until that rebuild lands, the only way to read it is to expand the fold. If the rebuild request fails (it is silently swallowed), the text stays buried.

This hurts most for skills/agents that ask the user a question mid-flow and end the turn waiting for the answer: the person staring at the chat sees "Working…" then a collapsed fold, and never learns they were asked anything.

Fix

Treat a surface post as conversation speech as soon as the UI can responsibly show it:

• postSpeechText(row, allowInFlight) (timeline): a post's text is speech once its result confirms delivery; live contexts may preview the in-flight text; failed or unconfirmed posts stay plain tool rows (consistent with the existing contract that an interrupted post must not claim it was delivered).
• Live dock (chat): an in-flight post row renders as a message icon + "Posting message" + the first line of the text, instead of the generic step label.
• Settled-but-pre-refresh timeline (chat): once the turn reaches a terminal status, confirmed posts flush the fold segment and render as work-said bubbles, so the text is visible the moment the turn ends without waiting for the transcript rebuild. The in-flight preview is gated on live work status, so an unconfirmed post never renders as speech inside a settled fold.

Posts also stop inflating the "N tool calls" fold count, which now reflects only actual tool work.

Testing

• New unit tests for postSpeechText (delivered / in-flight / failed / non-post shapes).
• Source-structure pins on both render sites and the dock branch, matching the repo's existing chat-source test idiom.
• plugins/web-ui suite: 597/597 green; tsc + oxlint clean.

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