refactor(wayland): extract clipboard runtime

[devmobasa]

Summary

• Add ClipboardRuntime to own the selection publish/paste, hex-copy, text-copy, and text-paste workers.
• Move single-flight submission and queue policies into the owner.
• Preserve clipboard generation and revision checks, paste supersession, queued-target rebasing, compositor-facing work, completion application, and toast behavior.
• Replace stringly copy and paste completions with the B-09 HexCopyOutcome, TextCopyOutcome, and TextPasteOutcome enums.
• Add focused owner tests for copy coalescing, cut preservation, paste-session supersession, active-paste deferral, target rebasing, and typed messages.

Stack

1 of 2. Base: main.

Validation

• cargo test --all-features
• cargo test --no-default-features
• cargo fmt --all -- --check
• Strict Clippy in both feature matrices reports only the known Rust 1.98 baseline diagnostics.
• Reviewed after rebase; the current tree is byte-identical to the reviewed tree.

Manual validation

Clipboard copy and paste require a hands-on check under a real Wayland compositor.