[FEATURE]:Add a copy action for tool output blocks

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Describe the enhancement you want to request

Add a copy action for tool output blocks

Description

It would be useful to have a Copy action for tool output blocks in the TUI.

Tool output is often collapsed behind Click to expand, for example output from git diff, logs, shell commands, etc. Currently, copying this output requires expanding the block and selecting the text manually in the terminal.

A copy action directly on the block would make this much easier.

Ideally, copying a collapsed block should copy the full tool output, not only the currently visible preview.

Example

Screenshot attached.

A small Copy action next to Click to expand (or another appropriate place in the block UI) would solve the problem.

Additional idea

Exposing the same action as a TUI command/keybind (for example, copy_tool_output) would also be useful.