fix(tui): sync copy selection via OSC52

[capt-marbles]

Summary

Fixes copy-selection auto-copy behavior in browser-backed terminals such as cmux by emitting OSC 52 clipboard escape sequences in addition to existing host clipboard integrations.

Why

The current copy_to_clipboard path can succeed via wl-copy/arboard while only updating the remote host clipboard. In cmux/web terminals, users expect drag auto-selection copy to update the browser/local clipboard. OSC 52 is the terminal-native clipboard synchronization mechanism supported by many terminal frontends.

Changes

• Emit OSC 52 clipboard sequence whenever Jcode copies selected text.
• Preserve existing wl-copy and arboard behavior.
• Add tmux passthrough wrapping for OSC 52 sequences.
• Add unit tests for OSC 52 sequence formatting.

Validation

• cargo fmt
• cargo test clipboard_tests::osc52_clipboard_sequence --lib
• cargo test test_copy_selection_mouse_drag_auto_copies_and_exits_mode --lib