Give each queued follow-up its own row

[shreeve]

Summary

Queued follow-ups in the composer painted over each other whenever one of them spanned more than one line.

Each row in the queued-message card was a fixed 30px box with its content vertically centred and truncate to keep the text on one line. truncate only stops soft wrapping: a hard newline still breaks the text into several lines, and centring those in 30px draws the extra lines over the rows above and below, and past the card's top edge. Any pasted terminal output or file tree in a follow-up did this.

This PR makes each row its own box:

• the row grows to its text and clips anything past that, so it can never paint over its neighbours;
• the queue icon and the controls are top-aligned with the first line instead of centred;
• a hairline rule separates consecutive rows;
• the text keeps its hard line breaks and wraps long lines, up to three lines with an ellipsis on the last, so a prompt is recognisable without the queue turning into a second transcript.

A one-line row still measures 30px, so the common case looks exactly as it did.

Before

Three queued prompts, the first two multi-line. Rows overlap and the first spills above the card:

After

Same three prompts with this change. Each row is bounded, top-aligned, and separated by a rule; the file tree is clamped to three lines:

Test plan

• cargo test --lib: 372 passed
• Reproduced in Waku Debug.app on main with three queued prompts (two multi-line), then confirmed the layout above after the rebuild with the same queue
• Single-line queued prompts unchanged at 30px

[shreeve]

The Ubuntu job here fails before any Rust runs: apt-get update on the runner image hits Google's Chrome apt repository and gets a Hash Sum mismatch, so "Install Linux dependencies" exits 100. It has failed the same way on three consecutive runs, and macOS passes on the same commit.

#220 removes that apt source from the workflow, so this PR needs #220 merged first before its CI can complete. Once #220 is in, I'll rebase this branch onto main and CI should go green.