fix(pty-proxy): scope proxy screen restore to its own terminal via ex…

[davidolrik]

Summary

Fixes the redraw corruption reported in #3566: activating the atuin search popup inside a terminal multiplexer pane (e.g. herdr) paints content from outside the pane — sidebars, other panes — into it on exit.

Root cause

atuin pty-proxy mirrors the shell's output into a vt100 screen model and serves snapshots over a unix socket, exporting ATUIN_PTY_PROXY_SOCKET and ATUIN_PTY_PROXY_ACTIVE=1 into the shell's environment. Environment variables are inherited by every descendant, so a multiplexer launched from a proxied shell passes both into every pane it creates.

The init guard only started a fresh proxy when ATUIN_PTY_PROXY_ACTIVE was
unset or $TMUX changed, so panes of any non-tmux multiplexer kept pointing at
the outer proxy. atuin search popup mode then fetched the outer proxy's
full-terminal screen — including the multiplexer's chrome — and
restore_popup_area blitted those full-width rows into the pane on exit.

Fix

We now export ATUIN_PTY_PROXY_TTY, and whenever the shells tty differes from it we spawn a new proxy.
This means that any multiplexer that uses a new tty for each pane will get a new pty-proxy for each pane.

As I am not a rust expert, I had a bit of help from Claude.

Closes #3566

Checks

• I am happy for maintainers to push small adjustments to this PR, to speed up the review cycle
• I have checked that there are no existing pull requests for the same thing

[greptile-apps]

Greptile Summary

This PR scopes pty-proxy screen restoration to the terminal that owns the snapshot. The main changes are:

• Exports the proxy PTY device to child shells.
• Starts a new proxy when shell and proxy TTY devices differ.
• Checks TTY identity and terminal dimensions before restoring a popup.
• Reconciles terminal size when the resize handler starts.
• Adds tests for proxy environment and TTY guard behavior.

Confidence Score: 4/5

Unknown proxy TTY ownership can still allow a foreign screen snapshot to be restored.

• Known, differing TTY devices are rejected correctly.
• Legacy sockets and PTY backends without a device name use dimensions alone.
• Same-sized multiplexer surfaces can therefore reproduce the redraw corruption.

crates/atuin/src/command/client/search/interactive.rs

Important Files Changed

Filename	Overview
Cargo.toml	Enables the rustix termios feature used for terminal-name lookup.
crates/atuin-pty-proxy/src/pty_proxy.rs	Adds TTY-aware proxy startup guards for Bash, Zsh, Fish, and Nushell.
crates/atuin-pty-proxy/src/runtime.rs	Exports the proxy slave TTY and applies the current terminal size when resize handling starts.
crates/atuin/src/command/client/search/interactive.rs	Validates popup snapshots by TTY and size, but falls back to size alone when TTY ownership is unknown.

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