On X11, don't panic when setting WM hints for user attention fails

[warp-agent-staging]

On X11, Window::request_user_attention panicked when WmHints::set failed to send its request, for example after the X connection died. Warp calls this to ring the bell while its window is inactive, so a dead connection aborted the app (Sentry WARP-CLIENT-BETA-STABLE-89S1). The send error is now logged with tracing::warn! and the call returns. When the send succeeds, the cookie is still dropped with ignore_error(), as before.

The branch is based on a4e0ecb5, the revision Warp pins today, so Warp can take the fix without also picking up the later commits on warpdotdev/v0.30.x. Warp picks up this commit in warpdotdev/warp-for-benchmarks#47. Other expect_then_ignore_error call sites in the X11 backend are unchanged.

• Tested on all platforms changed: X11 only. cargo check and cargo clippy --no-default-features --features x11,rwh_06 are clean. No test covers the dead-connection path, because it needs a live X server that disconnects mid-call.
• Added an entry to the changelog module: fork-only fix, no upstream changelog entry.
• Updated documentation: no user-facing API change.
• Created or updated an example program: not applicable.
• Updated feature matrix: no new features.

[warp-agent-staging]

This PR was generated with Warp.

Comment @warp-staging-factory on this PR to send it follow-up work.