Three SPA polish bugs reported against v1.0.1, all addressed in this PR;
no API / contract / schema change.

#570 — list filter row wrap (FilterBar trailing slot)
-----------------------------------------------------
The trailing slot rendered its children inside a sub-wrapper
"<div className=ml-auto flex flex-wrap>" — which behaved as one
flex item in the outer container. When the filter pills wrapped
onto a second line, the trailing wrapper wrapped as a unit and
ml-auto pushed it to the right edge of the new (empty) line —
producing the visually-separate "second toolbar row" the pilot
reported.

Fix: render the trailing children as DIRECT siblings of the
pills, no sub-wrapper. React.Children.toArray + cloneElement
injects ml-auto on the first non-null trailing child to push the
cluster right; flex-wrap then keeps the trailing buttons glued
to the end of the last pill row, never on a separate line.

#571 — per-object actions on detail (single-pk semantics)
---------------------------------------------------------
PR #562 (closing #555) wired the detail page to the CHANGELIST
actions endpoint with a one-pk array. That was the wrong
primitive: bulk-action verbs (selected files, selected items)
are list semantics and confused the operator on a single-object
page, and the per-object change_actions from
django-object-actions (which the API already surfaces as
data.object_actions) were visually buried.

Fix: drop the changelist-actions rendering from DetailPage
entirely. ObjectActionButton (already wired to runObjectAction
→ POST app/model/pk/action/name/) remains; it is the correct
single-pk primitive. Side effect: ~1.4 kB drop in the SPA
bundle from removing the unused useList, runAction,
confirm-modal, and runner code paths.

#572 — detail header layout (title squeezed, toolbar not right-aligned)
-----------------------------------------------------------------------
The header used sm:justify-between with no width hint on either
side, so the title block + toolbar block split horizontal space
roughly 50/50 even when the title needed more and the toolbar
would fit in less. The toolbar block had flex flex-wrap but no
justify-end, so wrapped button rows were left-aligned within the
right column — reading as "centered between title and viewport"
rather than "right-aligned to the page".

Fix: title block → min-w-0 flex-1 (claims all available width,
truncates only when it has to). Toolbar block →
shrink-0 flex-wrap justify-end. Toolbar only pushes the title
when its content genuinely needs the room, and wrapped button
rows hug the right edge.

Closes #570, #571, #572.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>