feat(core): fill the unified search pending window with placeholders

[pringelmann]

Summary

The new unified search bar clears its results on every keystroke, so the panel collapses to the filter row for the debounce plus the request, then jumps back down as category results arrive. Two jumps per letter typed.

Now it maintains the height it had and fills the gap with skeleton placeholders: a heading bar, then result-height rows. Resizes now also animate instead of snapping. (respecting user's preferred motion setting)

For now only the first skeleton heading is drawn. Where the next one goes depends on how many results a category returns, and a heading in the wrong spot looks worse than a plain bar. We can iterate on this after release.

Before

Kooha-2026-08-18-08-51-13.webm

After

Kooha-2026-08-18-08-49-52.webm

-> Preview link <-

u: bob p: bob

Manually tested

• Safari (16.5)
• Firefox
• Chromium

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI (CSS animations, tests)

[pringelmann]

Default derived from three providers with one result each. We can tweak this over time if its too jumpy.

Another solution is to keep a running average height stored in localstorage, but that feels like overkill

[pringelmann]

Or not show any placeholders at all on first search (empty list with only loading spinner indicating state)

[artonge]

Some comments seem superfluous

[kra-mo]

Amazing! Works really really well :)

[kra-mo]

I guess one tiny nit is that when there is only space for one result, only the header is shown, maybe some off by 1/greater-equals thing in the layouting?

[pringelmann]

Some comments seem superfluous

Shortened them and removed some

[pringelmann]

I guess one tiny nit is that when there is only space for one result, only the header is shown, maybe some off by 1/greater-equals thing in the layouting?

Fixed: there is now a minimum skeleton loader height