Treat X11 WM hints send failure as recoverable

[warp-agent-staging]

A failed X11 WmHints::set send can indicate that the connection closed while an application requested user attention. Treat that send failure as recoverable instead of panicking; successful sends still discard the void cookie's server-side result.

Warp consumes this revision in warpdotdev/warp-for-benchmarks#56.

Validation

• cargo test --manifest-path /workspace/winit/Cargo.toml --lib --no-default-features --features x11 — 8 tests passed.
• cargo clippy --manifest-path /workspace/winit/Cargo.toml --lib --no-default-features --features x11 -- -D warnings — passed.
• cargo fmt --manifest-path /workspace/winit/Cargo.toml --all -- --check — blocked by existing repository-wide formatting differences because the available stable rustfmt cannot apply this checkout's nightly-only options. The changed hunk passes git diff --check.
• No dedicated regression test: producing this send-time error requires closing a live X11 connection beneath the window object; the targeted X11 build and tests cover compilation of the changed path.

[warp-agent-staging]

This PR was generated with Warp.

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