#23843 Agent chat: never fold a finished turn's reply into Worked for

On nightly 331e2e9, a finished turn's final reply was drawn inside its "Worked for 1m 7s" fold. Leo: "Those replies should never be collapsed."

Why

answerAt (conversation/turns.ts) took a turn's answer to be the text it ended on. If a tool call came after that text, the turn had no answer, so the reply folded with the work.

What changed

• A finished turn's answer is now its last reply, even when work comes after it.
• Work after the reply (tool rows and interim notes) folds with the rest, so the reply stays the turn's last words below the fold.
• Only short interim notes that the turn worked on after (≤160 characters, one paragraph, no code; the existing isShortNote) count as status, and they still fold.
• When work comes after the reply, "Worked for" times the whole turn rather than stopping at the reply.

Changelog

• Fixed: a finished agent chat turn's reply is never folded into "Worked for", even when the agent ran a tool after it.

Tests

test/transcript-worked-fold.test.ts; the test commit 631639bb comes before the fix:

• a reply that a tool ran after stays open below the fold, the tool folds, and the opened fold holds every tool row of the turn in order and never the reply;
• the last reply stays open when short notes and tools come after it.

The existing cases are unchanged: interim short notes followed by a tool still fold, a turn stopped mid-tool still folds, and an edit after the answer still joins the edit card.

Observed / Not run

• Observed: Leo's screenshot of nightly 331e2e9, with the reply inside the open "Worked for 1m 7s" fold under "Ran defaults read …".
• Not run locally: the unit tests, the type checker and the gallery. They run in this PR's CI (this Mac does not build). The base-red run of the new tests is CI's run on 631639bb.
  No capture: webview transcript shaping change, covered by unit tests; the gallery advisory run captures the transcript entries.

Agent session: cosmic-gray

🤖 Generated with Claude Code

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Summary by cubic

Fixes agent chat transcript shaping so a finished turn's final reply is never collapsed into its "Worked for" fold, even when the agent ran a tool after replying.

Bug Fixes

• A finished turn's answer is now its last reply; tool rows and interim notes after it fold with the rest so the reply stays the turn's last words.
• Only short interim notes (≤160 characters, one paragraph, no code) count as status and still fold.
• "Worked for" now times the whole turn when work came after the reply, instead of stopping at the reply.