Turn title font size too large and overflows title bar

[dnviti]

Problem / Motivation

When a conversation turn is collapsed, the summary title shown on its header bar renders at the wrong font size — noticeably larger than every other piece of text in that bar — and a long title spills outside the bar instead of staying inside it. Measured on a narrow window, a long title fills roughly three lines of content inside a bar only tall enough for one, pushing the text over the surrounding UI.

This is a regression introduced in 5.1.2: before the collapsible-turns change, a collapsed turn's title was not displayed on that bar at all, so the sizing and overflow problem arrives with it.

Goal

A collapsed turn's title reads as part of its header bar — same compact text size as the rest of the bar — and a long title is cut off with an ellipsis instead of overflowing.

Scope

• Correct the font size of the collapsed-turn title so it matches the other text in the same bar.
• Truncate a long title with an ellipsis, keeping it on one line so it never grows or escapes the bar.
• Extend the automated layout checks to cover a collapsed turn with a long title. Today's checks only ever measure an expanded turn, which is why this shipped unnoticed.

Non-goals

• No change to how turn titles are worded or generated.
• No change to the bar's height, layout, or the collapse/expand behaviour itself.
• The other small status text in that bar (tool and reasoning counts) is already sized and truncated correctly and needs no change.

Acceptance Criteria

• A collapsed turn's title renders at the same compact size as the rest of its header bar.
• A turn with a very long title is truncated with an ellipsis, stays on one line, and never overflows the bar — verified at narrow, medium, and wide window widths.
• Short titles still display in full, unchanged.
• An automated layout check fails if a collapsed turn's long title ever overflows its bar again.

[dnviti]

Fixed on the 5.1.2 release branch in #49 (merged as dc6ddf0).

The collapsed turn's title now sets both an explicit size and nowrap — without the latter the ellipsis was inert, which is why a long title wrapped and left the bar rather than being cut.

Worth recording: this only ever rendered on a collapsed turn, and the layout check's fixture had a single turn, which is never collapsed — so the broken element was never rendered during the check at all. The fixture now has a second turn, and the check was confirmed to fail against the unfixed code (68px of content in a 28px bar at 924px). The browser checks also now run in CI, which they previously did not.

Leaving this open until 5.1.2 reaches main.

[dnviti]

Fixed in #49 (dc6ddf0), on the 5.1.2 release branch. Closing as requested — it will ship with 5.1.2.