[BUG] TUI mouse-selection copy strips rich clipboard flavors (no public.html)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

When I select text with the mouse inside the Claude Code TUI and copy it (via Ghostty's copy-on-select or an explicit ⌘C), the clipboard receives only plain-text flavors — the terminal's rich public.html flavor is missing. Selecting and copying the same text outside the TUI (at a plain shell prompt, same Ghostty window) does produce public.html. So the TUI's selection capture is intercepting the selection and writing plain text only.

Evidence via osascript -e 'clipboard info':

• Inside TUI: «class utf8», «class ut16», string, Unicode text — no «class HTML»
• Outside TUI (shell prompt, same window): includes «class HTML»

This silently breaks downstream tooling that reconstructs formatting (bold, inline code) from the styled clipboard flavor — there's nothing styled left to reconstruct from.

What Should Happen?

Copying a TUI selection should preserve the terminal's rich clipboard flavors (e.g. public.html), the same way a native terminal selection does — or there should be a setting to disable the TUI's selection capture and fall back to terminal-native selection/copy.

Error Messages/Logs

_None._

Steps to Reproduce

1. Ghostty 1.3.1 on macOS (copy-on-select enabled; ⌘C also reproduces).
2. In a Claude Code session, mouse-select assistant output that contains styled text (bold / inline code).
3. Copy (⌘C).
4. Run osascript -e 'clipboard info' → only plain-text flavors; no «class HTML».
5. Control: drop to a plain shell prompt (outside the TUI) in the same window, select text, ⌘C, osascript -e 'clipboard info' → «class HTML» present.

Claude Model

Not sure / Multiple models _(bug is model-independent)_

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — possibly tied to the mouse-selection rework around v2.1.187 (see #71085)

Claude Code Version

2.1.197

Platform

Anthropic API

Operating System

macOS (15.7.7, build 24G720)

Terminal/Shell

Other — Ghostty 1.3.1

Additional Information

• The terminal itself still emits public.html for native selections (control test above), so the change is on the Claude Code side, not Ghostty.
• Possibly related: #71085 ("Mouse text selection and history scroll broken in MobaXterm after v2.1.187") — may share the same TUI selection-handling change.