Match the desktop composer skeleton to the loaded composer #275

Problem

On desktop, the composer skeleton is 8 px shorter than the composer that replaces it. When the composer loads, its top edge rises 8 px, and the feed above it loses 8 px of height.

On 14ab7f9c1. Paths are under apps/webapp/src/components/chatroom/components/.

The phone skeleton already matches the row height: min-h-11 gap-1 px-3 py-2 on the row, and size-11 on each button placeholder.

Steps to reproduce

1. On desktop, open a pad.
2. In DevTools, add a network throttling profile with 10,000 ms latency, and select it.
3. Open a heading chat as a channel member.
4. When the composer skeleton turns into the composer, see the composer's top edge move up.

Acceptance criteria

• On desktop, test the idle state: an empty draft, no reply, edit, or comment bar, no attachments, and the format toolbar closed. In that state, the skeleton and the loaded composer have the same outer height, button positions, and field height.
• The composer's top edge has the same getBoundingClientRect().top just before and just after the swap.
• The phone skeleton does not change.

Agent Brief

Category: bug
Summary: Size the desktop composer skeleton row like the loaded composer row.

Current behavior:
The desktop skeleton row uses smaller padding and 28 px button placeholders, so it is 40 px tall. The loaded row is 48 px tall.

Desired behavior:
The desktop skeleton uses the loaded row's padding and gap, 32 px button placeholders, and a 32 px field placeholder. The composer's top edge does not move at the swap.

Key interfaces:

• ChatroomComposerSkeleton({ variant }).
• ComposerBar — the loaded composer bar. Its input row is the reference.

Out of scope

• The phone skeleton, including the 2 px gap difference between its emoji and send placeholders.
• Skeletons outside the composer.
• When the skeleton shows, including after a load error, tracked in Drop the composer and participants skeletons when the channel data load fails #283.

Notes

The evidence is a class comparison on 14ab7f9c1. The heights follow Tailwind's scale and were not measured in a browser.