Two things, one title.
The pane's header is now editable and calls the same `renameSession` the list's pencil does, so both
surfaces write the transcript's `summary` line and the invalidation that follows refreshes the row. The
id comes from the URL rather than `resumeSessionId`: they agree for an ordinary conversation and not for
a merged `/clear` chain, where the resume target is the tail while the list and the server address the
chain by its head — renaming the tail would have written a title nothing displays. `/chat/new` has no
transcript yet, so there the title is read-only.
And on `/chat/<id>` the conversation names the page, sitting between a typed tab name and the route
default: `label ?? override ?? titleForPath()`. Naming a window is deliberate and must still win. Not
gated on full screen, though that is where it earns its keep — the nav header is hidden there, so the
browser tab strip is the only thing telling two side-by-side windows apart. Tiled, the same value fills
the header's centre.
The edit interaction is now one `EditableTitle` shared with the nav header instead of a second copy of
it. `allowEmpty` is what keeps the header's "clear it to hand the tab back to the route name" working;
everywhere else empty means keep, since the rename endpoint 400s on it. `SessionList`'s row rename is
deliberately NOT folded in — it opens from a pencil and confirms with a check, so it is a different
interaction wearing the same styling.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>